 Research
 Open Access
 Published:
Asymptotic behavior of thirdorder differential equations with nonpositive neutral coefficients and distributed deviating arguments
Advances in Difference Equations volume 2016, Article number: 105 (2016)
Abstract
Using the Riccati transformation technique, we present several sufficient conditions that guarantee that all solutions to a thirdorder differential equation with nonpositive neutral coefficients and distributed deviating arguments are either oscillatory or converge to zero asymptotically. In particular, we establish Hille and Nehari type criteria. Two examples are given to demonstrate the practicability of the main results.
Introduction
Thirdorder differential equations have attracted noticeable interests due to their potential applications in assorted fields, including physical sciences, technology, population dynamics, and so on. Recently, the qualitative theory of thirdorder differential equations has become an interesting topic, and there have been some results on the oscillatory and asymptotic behavior of thirdorder equations; see, for example, the monographs [1, 2], the papers [3–23], and the references therein. In particular, it is a necessary and valuable issue, either theoretically or practically, to investigate differential equations with distributed deviating arguments; see the papers by Tian et al. [21], Wang [24], and Wang and Cai [25]. On the basis of these background details, the objective of this paper is to analyze the oscillation and asymptotic properties of a class of thirdorder neutral differential equations
where \(t \geq t_{0}>0\), \(z(t):=x(t)\int_{a}^{b}p(t,\mu)x[\tau(t,\mu )]\,d\mu\), \(\alpha>0\) is a quotient of odd positive integers, \(r(t)\in C^{1}([t_{0},\infty),(0,\infty))\), \(\int_{t_{0}}^{\infty}r^{1/\alpha}(t)\,dt=\infty\), \(p(t,\mu)\in C([t_{0},\infty)\times[a,b],\mathbb{R})\), \(0\leq\int_{a}^{b}p(t,\mu)\,d\mu\leq p_{0}<1\), \(\tau(t,\mu)\in C([t_{0},\infty)\times[a,b],\mathbb{R})\), \(\tau(t,\mu)\leq t\), \(\liminf_{t\rightarrow\infty}\tau(t,\mu)=\infty\) for \(\mu\in[a,b]\), \(q(t,\xi)\in C([t_{0},\infty)\times[c,d],[0,\infty))\), \(q(t,\xi)\) is not identically zero for large t, \(\sigma(t,\xi)\in C([t_{0},\infty)\times[c,d],\mathbb{R})\) is a nondecreasing function for ξ satisfying \(\sigma(t,\xi)\leq t\) and \(\liminf_{t\rightarrow\infty}\sigma(t,\xi)=\infty\) for \(\xi\in[c,d]\), \(f(x)\in C(\mathbb{R}, \mathbb{R})\), and there exists a positive constant k such that \(f(x)/x^{\alpha}\geq k\) for all \(x\neq0\).
We assume that solutions of (1.1) exist for any \(t\in[t_{0},\infty)\). Our attention is restricted to those solutions of (1.1) that are not identically zero for large t. As usual, a solution of (1.1) is called oscillatory if it has arbitrarily large zeros on the interval \([t_{0},\infty)\). Otherwise, it is termed nonoscillatory (i.e., it is either eventually positive or eventually negative).
It is known that analysis of neutral differential equations is more difficult in comparison with that of ordinary differential equations, although certain similarities in the behavior of solutions of these two classes of equations are observed; see, for example, [1, 2, 6, 8–10, 12, 13, 16–18, 20–24, 26–30] and the references therein. Assuming that
and
asymptotic criteria for (1.1) have been reported in [20, 21, 23]. So far, there are few results dealing with the asymptotic properties of thirdorder differential equations with nonpositive coefficients; we refer the reader to [6, 18, 22]. In particular, Baculíková and Džurina [6] and Zhang et al. [22] established several Hille and Nehari type (see Agarwal et al. [4]) criteria for the equation
under the assumptions that \(0\leq p(t)\leq p_{0}<1\) and (1.2) holds.
It should be noted that condition (1.2) is a restrictive condition in the study of asymptotic behavior of thirdorder differential equations. To solve this problem without requiring (1.2), Li et al. [17] obtained some oscillation criteria for a thirdorder neutral delay differential equation
by employing the Riccati substitution
where \(0\leq p(t)\leq p_{0}<1\), \(z(t):=x(t)+p(t)x(\tau(t))\), and \(\rho (t)\in C^{1}([t_{0},\infty),(0,\infty))\). A natural question now is: is it possible to establish asymptotic tests for (1.1) without requiring restrictive condition (1.2)? Motivated by Baculíková and Džurina [6], Li et al. [17], and Zhang et al. [22], the principal goal of this paper is to give an affirmative answer to this question. In Section 2, some lemmas are provided to prove the main results. In Section 3, some oscillation results for (1.1) are obtained by using the Riccati transformation technique, and these results also can be applied to the cases where \(r'(t)\leq0\) or \(r'(t)\) is oscillatory. In Section 4, two illustrative examples are included. All functional inequalities considered in the sequel are tacitly assumed to hold for all t large enough.
Several lemmas
Lemma 2.1
Assume that \(x(t)\) is an eventually positive solution of (1.1). Then there exists a \(t_{1}\geq t_{0}\) such that, for \(t\geq t_{1}\), \(z(t)\) has the following four possible cases:

(i)
\(z(t)>0\), \(z'(t)>0\), \(z''(t)>0\), \((r(t)(z''(t))^{\alpha})'\leq0\);

(ii)
\(z(t)>0\), \(z'(t)<0\), \(z''(t)>0\), \((r(t)(z''(t))^{\alpha})'\leq0\);

(iii)
\(z(t)<0\), \(z'(t)<0\), \(z''(t)>0\), \((r(t)(z''(t))^{\alpha})'\leq0\);

(iv)
\(z(t)<0\), \(z'(t)<0\), \(z''(t)<0\), \((r(t)(z''(t))^{\alpha})'\leq0\).
Proof
Let \(x(t)\) be an eventually positive solution of (1.1). Then there exists a \(t_{1}\geq t_{0}\) such that, for \(t\geq t_{1}\),
It follows from (1.1) and the definition of \(z(t)\) that \(x(t)\geq z(t)\) and
Hence, \(r(t)(z''(t))^{\alpha}\) is nonincreasing and of one sign, which implies that \(z''(t)\) is also of one sign. Therefore, there exists a \(t_{2}\geq t_{1}\) such that, for \(t\geq t_{2}\), \(z''(t)<0\) or \(z''(t)>0\).
Case 1. The condition \(z''(t)<0\) yields that there exists a constant \(M>0\) such that
that is,
Integrating this inequality from \(t_{2}\) to t, we conclude that
Letting \(t\rightarrow\infty\), we have that \(z'(t)\rightarrow\infty\), and so \(z'(t)<0\) eventually. Note that the conditions \(z''(t)<0\) and \(z'(t)<0\) imply that \(z(t)<0\). Thus, we get case (iv).
Case 2. Assume that \(z''(t)>0\). Then \(z'(t)\) is of one sign. If \(z'(t)>0\), then \(z(t)>0\). If \(z'(t)<0\), then \(z(t)>0\) or \(z(t)<0\). Hence, we have three possible cases (i), (ii), and (iii) when \(z''(t)>0\). The proof is complete. □
Lemma 2.2
Assume that \(x(t)\) is an eventually positive solution of (1.1) and the corresponding \(z(t)\) satisfies case (i) in Lemma 2.1. Then there exist two numbers \(t_{1}\geq t_{0}\) and \(t_{2}> t_{1}\) such that, for \(t\geq t_{2}\),
and \(z'(t)/\int^{t}_{t_{1}}r^{1/\alpha}(s)\,ds\) is nonincreasing eventually.
Proof
Let \(z(t)\) satisfy case (i) in Lemma 2.1. Then
Hence, we deduce that
which implies that \(z'(t)/\int^{t}_{t_{1}}r^{1/\alpha}(s)\,ds\) is nonincreasing eventually, and so
This completes the proof. □
Lemma 2.3
Let \(x(t)\) be an eventually positive solution of (1.1) and assume that the corresponding \(z(t)\) satisfies case (ii) in Lemma 2.1. If
then \(\lim_{t\rightarrow\infty}x(t)=0\).
Proof
It follows from property (ii) that there exists a finite constant \(l\geq 0\) such that \(\lim_{t\rightarrow\infty}z(t)=l\). We claim that \(l=0\). Otherwise, assume that \(l>0\). By the definition of \(z(t)\), \(x(t)\geq{z(t)}>{l}\). An application of (1.1) yields
Integrating the latter inequality from t to ∞, we have
which implies that
Integrating this inequality from t to ∞ and then integrating the resulting inequality from \(t_{1}\) to ∞, we conclude that
which is a contradiction to (2.1). Hence, \(l=0\) and \(\lim_{t\rightarrow \infty}z(t)=0\).
Next, we prove that \(x(t)\) is bounded. If not, then there exists a sequence \(\{t_{m}\}\) such that \(\lim_{m\rightarrow\infty}t_{m}=\infty\) and \(\lim_{m\rightarrow \infty}x(t_{m})=\infty\), where \(x(t_{m}):=\max\{x(s); t_{0}\leq{s}\leq{t_{m}}\}\). Since \(\liminf_{t\rightarrow\infty}\tau(t,\mu)=\infty\), \(\tau(t_{m}, \mu)>t_{0}\) for all sufficiently large m. By \(\tau(t,\mu)\leq t\), we conclude that
and so
which yields \(\lim_{m\rightarrow{\infty}}z(t_{m})=\infty\). This contradicts \(\lim_{t\rightarrow{\infty}}z(t)=0\). Therefore, \(x(t)\) is bounded, and hence we may suppose that \(\limsup_{t\rightarrow{\infty}}x(t)=a_{0}\), where \(0\leq{a_{0}}<\infty\). Then, there exists a sequence \(\{t_{k}\}\) such that \(\lim_{k\rightarrow {\infty}}t_{k}=\infty\) and \(\lim_{k\rightarrow{\infty}}x(t_{k})=a_{0}\). Assuming now that \(a_{0}>0\) and letting \(\varepsilon :=a_{0}(1p_{0})/(2p_{0})\), we have \(x(\tau(t_{k},\mu))<{a_{0}+\varepsilon}\) eventually, and thus
which is a contradiction. Thus, \(a_{0}=0\) and \(\lim_{t\rightarrow\infty }x(t)=0\). The proof is complete. □
Main results
In what follows, we let
where the meaning of \(\rho(t)\) will be explained later.
Theorem 3.1
Assume that condition (2.1) is satisfied. If there exists a function \(\rho(t)\in C^{1}([t_{0},\infty),(0,\infty))\) such that, for all sufficiently large \(t_{1}\geq t_{0}\) and for some \(t_{3}> t_{2}>t_{1}\),
where
then every solution \(x(t)\) of (1.1) is either oscillatory or converges to zero as \(t\rightarrow\infty\).
Proof
Suppose to the contrary that (1.1) has a nonoscillatory solution \(x(t)\). Without loss of generality, we may assume that \(x(t)\) is eventually positive (since the proof of the case where \(x(t)\) is eventually negative is similar). By Lemma 2.1, we observe that, for \(t\geq t_{1}\geq t_{0}\), \(z(t)\) satisfies four possible cases (i), (ii), (iii), or (iv) (as those of Lemma 2.1). We consider each of the four cases separately.
Assume first that case (i) is satisfied. For \(t\geq{t_{1}}\), define the Riccati transformation \(\omega(t)\) by
Then \(\omega(t)>0\) for \(t\geq{t_{1}}\). Differentiation of (3.3) yields
It follows from (1.1) and (i) that
Using (3.3) and (3.5) in (3.4), we deduce that
Since \(\sigma_{*}(t)\leq t\) and \(z'(t)/\int^{t}_{t_{1}}r^{1/\alpha}(s)\,ds\) is nonincreasing (see Lemma 2.2), we have
that is,
It follows now from Lemma 2.2 and (3.7) that
where \(G(t)\) is defined by (3.2). Substituting (3.8) into (3.6), we get
Set
Using the inequality (see [15])
we have
Substituting the latter inequality into (3.9), we conclude that
Integrating this inequality from \(t_{3}\) (\(t_{3}>t_{2}\)) to t, we arrive at
which contradicts (3.1).
Suppose that case (ii) is satisfied. By Lemma 2.3, \(\lim_{t\rightarrow \infty}x(t)=0\).
If case (iii) or case (iv) holds, then \(\lim_{t\rightarrow\infty }z(t)=c_{0}<0\) (possibly \(c_{0}=\infty\)) or \(\lim_{t\rightarrow\infty}z(t)=\infty\), respectively. Proceeding similarly as in the proof of Lemma 2.3, we conclude that \(x(t)\) and \(z(t)\) are bounded. Hence, \(c_{0}\) is finite, and case (iv) does not occur. Similar analysis to that in Lemma 2.3 leads to the conclusion that \(\lim_{t\rightarrow\infty}x(t)=0\). This completes the proof. □
Letting \(\rho(t)=t\) and \(\rho(t)=1\), we can derive the following results from Theorem 3.1.
Corollary 3.1
Let condition (2.1) hold. If for all sufficiently large \(t_{1}\geq t_{0}\) and for some \(t_{3}> t_{2}>t_{1}\),
where \(G(t)\) is as in (3.2), then the conclusion of Theorem 3.1 remains intact.
Corollary 3.2
Let condition (2.1) be satisfied. If for all sufficiently large \(t_{1}\geq t_{0}\) and for some \(t_{3}> t_{2}>t_{1}\),
where \(G(t)\) is defined by (3.2), then the conclusion of Theorem 3.1 remains intact.
In what follows, we establish Hille and Nehari type criteria for (1.1). To this end, we introduce the following lemma.
Lemma 3.1
Let \(x(t)\) be an eventually positive solution of (1.1). Define
where \(G(t)\) is defined by (3.2), \(t_{1}\geq t_{0}\) is sufficiently large, and \(t_{3}> t_{2}>t_{1}\).

(I)
Let \(\bar{p}<\infty\), \(\bar{q}<\infty\), and suppose that the corresponding \(z(t)\) satisfies case (i) in Lemma 2.1. Then
$$ \bar{p}\leq\bar{r}\bar{r}^{1+{1}/{\alpha}}\leq\frac{\alpha^{\alpha }}{(\alpha+1)^{\alpha+1}} \quad\textit{and}\quad \bar{p}+\bar{q}\leq 1. $$(3.12) 
(II)
If \(\bar{p}=\infty\) or \(\bar{q}=\infty\), then \(z(t)\) does not have property (i) in Lemma 2.1.
Proof
Part (I). Assume that \(x(t)\) is an eventually positive solution of (1.1) and the corresponding \(z(t)\) satisfies (i). By (3.11), we have \(\omega(t)>0\) and
As in the proof of Theorem 3.1, we get (3.5) and (3.8), and so
On the other hand, we conclude that
due to the proof of Lemma 2.2. Hence,
which implies that \(0\leq\bar{r} \leq\bar{R} \leq1\) and \(\lim_{t\rightarrow\infty}\omega(t)=0\). Integrating (3.13) from t to ∞, we obtain
Multiplying (3.14) by \((\int^{t}_{t_{1}}r^{1/\alpha}(s)\,ds )^{\alpha}\), we deduce that
that is,
where
Now, for any \(\varepsilon>0\), there exists a \(t_{3}>t_{2}\) such that, for \(t\geq t_{3}\),
which yields
Applications of (3.15) and the definitions of r̄ and p̄ imply that
Since ε is arbitrary, we conclude that
Next, we prove that
Multiplying (3.13) by \((\int^{t}_{t_{1}}r^{1/\alpha}(u)\,du )^{\alpha+1}\) and integrating the resulting inequality from \(t_{3}\) to t, we have
Integrating by parts, we deduce that
where
Using inequality (3.10) with
we have
Thus, we arrive at
Taking the lim sup of both sides of the latter inequality as \(t\rightarrow\infty\), we have
It follows from (3.16) and (3.18) that
Moreover, by inequality (3.10),
Therefore, the desired inequalities in (3.12) hold. This completes the proof of Part (I).
Part (II). Let \(x(t)\) be an eventually positive solution of (1.1). We show that \(z(t)\) does not have property (i). Assume the contrary. Suppose first that \(\bar{p}=\infty\). Inequality (3.14) implies that
Taking the lim inf of both sides of the latter inequality as \(t\rightarrow\infty\), we arrive at
which is a contradiction. Assume now that \(\bar{q}=\infty\). An application of inequality (3.17) yields
which is also a contradiction. The proof of Part (II) is complete. □
On the basis of Lemma 3.1, we easily derive the following result with a proof similar to that of Theorem 3.1.
Theorem 3.2
Assume that condition (2.1) is satisfied. If for all sufficiently large \(t_{1}\geq t_{0}\) and for some \(t_{3}> t_{2}>t_{1}\),
or
where \(G(t)\) is defined by (3.2), p̄ and q̄ are as in Lemma 3.1, then the conclusion of Theorem 3.1 remains intact.
Examples
The following examples illustrate applications of the main results in this paper.
Example 4.1
For \(t\geq1\), consider the thirdorder differential equation
Let \(\alpha=1\), \(a=0\), \(b=\pi/2\), \(c=3\pi\), \(d=2\pi\), \(k=1\), \(r(t)=1\), \(p(t,\mu)=1/2\), \(\tau(t,\mu)=t\mu\), \(q(t,\xi)=1/4\), and \(\sigma(t,\xi)=t+\xi/2\). Note that
and
Furthermore, \(q_{*}(t)=\pi/4\) and
Hence, by Corollary 3.2, every solution \(x(t)\) of (4.1) is either oscillatory or converges to zero as \(t\rightarrow\infty\). As a matter of fact, \(x(t)=\sin t\) is an oscillatory solution to (4.1).
Example 4.2
For \(t\geq1\) and \(q_{0}>0\), consider the thirdorder differential equation
Let \(\alpha=1\), \(a=1\), \(b=2\), \(c=0\), \(d=1\), \(k=1\), \(r(t)=1\), \(p(t,\mu)=\mu/(t+1)\), \(\tau(t,\mu)=(t+\mu)/3\), \(q(t,\xi )=2q_{0}\xi/t^{3}\), and \(\sigma(t,\xi)=(t+\xi)/2\). Note that
and
Moreover,
\(q_{*}(t)=q_{0} t^{3}\), and
Using Theorem 3.2, every solution \(x(t)\) of (4.2) is either oscillatory or converges to zero as \(t\rightarrow\infty\) if \(q_{0}>2\).
Remark 4.1
Observe that Theorems 3.1 and 3.2 cannot distinguish solutions of (1.1) with different behaviors. It is not easy to obtain sufficient conditions that ensure that all solutions \(x(t)\) of (1.1) just satisfy \(\lim_{t\rightarrow\infty}x(t)=0\) and do not oscillate. Neither is it possible to utilize the technique exploited in this work for proving that all solutions of (1.1) are oscillatory. Therefore, two interesting problems for future research can be formulated as follows.
References
 1.
Bainov, DD, Mishev, DP: Oscillation Theory for Neutral Differential Equations with Delay. Hilger, Bristol (1991)
 2.
Erbe, LH, Kong, QK, Zhang, BG: Oscillation Theory for Functional Differential Equations. Dekker, New York (1995)
 3.
Agarwal, RP, Bohner, M, Li, T, Zhang, C: Oscillation of thirdorder nonlinear delay differential equations. Taiwan. J. Math. 17, 545558 (2013)
 4.
Agarwal, RP, Bohner, M, Li, T, Zhang, C: Hille and Nehari type criteria for thirdorder delay dynamic equations. J. Differ. Equ. Appl. 19, 15631579 (2013)
 5.
Aktaş, MF, Çakmak, D, Tiryaki, A: On the qualitative behaviors of solutions of thirdorder nonlinear functional differential equations. Appl. Math. Lett. 24, 18491855 (2011)
 6.
Baculíková, B, Džurina, J: Oscillation of thirdorder neutral differential equations. Math. Comput. Model. 52, 215226 (2010)
 7.
Baculíková, B, Džurina, J: Oscillation of thirdorder nonlinear differential equations. Appl. Math. Lett. 24, 466470 (2011)
 8.
Candan, T: Asymptotic properties of solutions of thirdorder nonlinear neutral dynamic equations. Adv. Differ. Equ. 2014, 35 (2014)
 9.
Candan, T: Oscillation criteria and asymptotic properties of solutions of thirdorder nonlinear neutral differential equations. Math. Methods Appl. Sci. 38, 13791392 (2015)
 10.
Candan, T, Dahiya, RS: Oscillation of third order functional differential equations with delay. In: Proceedings of the Fifth Mississippi State Conference on Differential Equations and Computational Simulations. Electron. J. Differ. Equ. Conf., vol. 10, pp. 7988 (2003)
 11.
Grace, SR, Agarwal, RP, Pavani, R, Thandapani, E: On the oscillation of certain third order nonlinear functional differential equations. Appl. Math. Comput. 202, 102112 (2008)
 12.
Han, Z, Li, T, Zhang, C, Sun, S: Oscillatory behavior of solutions of certain thirdorder mixed neutral functional differential equations. Bull. Malays. Math. Soc. 35, 611620 (2012)
 13.
Jiang, Y, Li, T: Asymptotic behavior of a thirdorder nonlinear neutral delay differential equation. J. Inequal. Appl. 2014, 512 (2014)
 14.
Li, T, Han, Z, Sun, S, Zhao, Y: Oscillation results for third order nonlinear delay dynamic equations on time scales. Bull. Malays. Math. Soc. 34, 639648 (2011)
 15.
Li, T, Rogovchenko, YuV: Asymptotic behavior of an oddorder delay differential equation. Bound. Value Probl. 2014, 107 (2014)
 16.
Li, T, Rogovchenko, YuV: Asymptotic behavior of higherorder quasilinear neutral differential equations. Abstr. Appl. Anal. 2014, 395368 (2014)
 17.
Li, T, Zhang, C, Xing, G: Oscillation of thirdorder neutral delay differential equations. Abstr. Appl. Anal. 2012, 569201 (2012)
 18.
Qiu, YC: Oscillation criteria of thirdorder nonlinear dynamic equations with nonpositive neutral coefficients on time scales. Adv. Differ. Equ. 2015, 299 (2015)
 19.
Saker, SH, Džurina, J: On the oscillation of certain class of thirdorder nonlinear delay differential equations. Math. Bohem. 135, 225237 (2010)
 20.
Şenel, MT, Utku, N: Oscillation criteria for thirdorder neutral dynamic equations with continuously distributed delay. Adv. Differ. Equ. 2014, 220 (2014)
 21.
Tian, Y, Cai, Y, Fu, Y, Li, T: Oscillation and asymptotic behavior of thirdorder neutral differential equations with distributed deviating arguments. Adv. Differ. Equ. 2015, 267 (2015)
 22.
Zhang, C, Saker, SH, Li, T: Oscillation of thirdorder neutral dynamic equations on time scales. Dyn. Contin. Discrete Impuls. Syst., Ser. B, Appl. Algorithms 20, 333358 (2013)
 23.
Zhang, QX, Gao, L, Yu, YH: Oscillation criteria for thirdorder neutral differential equations with continuously distributed delay. Appl. Math. Lett. 25, 15141519 (2012)
 24.
Wang, PG: Oscillation criteria for secondorder neutral equations with distributed deviating arguments. Comput. Math. Appl. 47, 19351946 (2004)
 25.
Wang, PG, Cai, H: Oscillatory criteria for higher order functional differential equations with damping. J. Funct. Spaces Appl. 2013, 968356 (2013)
 26.
Bohner, M, Li, T: Oscillation of secondorder pLaplace dynamic equations with a nonpositive neutral coefficient. Appl. Math. Lett. 37, 7276 (2014)
 27.
Dong, JG: Oscillation behavior of second order nonlinear neutral differential equations with deviating arguments. Comput. Math. Appl. 59, 37103717 (2010)
 28.
Li, Q, Wang, R, Chen, F, Li, T: Oscillation of secondorder nonlinear delay differential equations with nonpositive neutral coefficients. Adv. Differ. Equ. 2015, 35 (2015)
 29.
Li, T, Rogovchenko, YuV: Oscillation of secondorder neutral differential equations. Math. Nachr. 288, 11501162 (2015)
 30.
Zhang, C, Agarwal, RP, Bohner, M, Li, T: Oscillation of secondorder nonlinear neutral dynamic equations with noncanonical operators. Bull. Malays. Math. Soc. 38, 761778 (2015)
Acknowledgements
The authors express their sincere gratitude to the editors and two anonymous referees for careful reading of the manuscript and valuable suggestions that helped to improve the paper. This research is supported by NNSF of P.R. China (Grant Nos. 61503171, 61403061, and 11447005), CPSF (Grant No. 2015M582091), NSF of Shandong Province (Grant No. ZR2012FL06), DSRF of Linyi University (Grant No. LYDX2015BS001), and the AMEP of Linyi University, P.R. China.
Author information
Additional information
Competing interests
The authors declare that they have no competing interests.
Authors’ contributions
All three authors contributed equally to this work. They all read and approved the final version of the manuscript.
Rights and permissions
Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
About this article
Received
Accepted
Published
DOI
MSC
 34K11
Keywords
 asymptotic behavior
 thirdorder neutral differential equation
 nonpositive neutral coefficient
 distributed deviating argument
 oscillation