[5] Berezansky, L. M.: 
Development of N. V. Azbelev's $W$-method in problems of the stability of solutions of linear functional-differential equations. Differ. Equations 22 (1986), 521-529 translation from Differ. Uravn. 22 1986 739-750 Russian. 
MR 0846501 | 
Zbl 0612.34069[11] Burton, T. A.: 
Stability by Fixed Point Theory for Functional Differential Equations. Dover Publications, Mineola (2006). 
MR 2281958 | 
Zbl 1160.34001[12] Cahlon, B., Schmidt, D.: 
An algorithmic stability test for neutral first order delay differential equations with $M$ commensurate delays. Dyn. Contin. Discrete Impuls. Syst., Ser. A, Math. Anal. 23 (2016), 1-26. 
MR 3453288 | 
Zbl 1333.34112[14] Gopalsamy, K.: 
A simple stability criterion for linear neutral differential systems. Funkc. Ekvacioj, Ser. Int. 28 (1985), 33-38. 
MR 0803401 | 
Zbl 0641.34069[16] Gusarenko, S. A., Domoshnitsky, A. I.: 
Asymptotic and oscillation properties of first-order linear scalar functional-differential equations. Differ. Equations 25 (1989), 1480-1491 translation from Differ. Uravn. 25 1989 2090-2103 Russian. 
MR 1044645 | 
Zbl 0726.45011[17] Györi, I., Ladas, G.: 
Oscillation Theory of Delay Differential Equations: With Applications. Clarendon Press, Oxford (1991). 
MR 1168471 | 
Zbl 0780.34048[27] Wu, J., Yu, J. S.: 
Convergence in nonautonomous scalar neutral equations. Dyn. Syst. Appl. 4 (1995), 279-290. 
MR 1338949 | 
Zbl 0830.34066