Explicit asymptotic stability criteria for neutral differential equations with two delays. Ren, Hongshan, Li, Hongyan (2002) Applied Mathematics E-Notes [electronic only]
Exponential stability and estimation of solutions of linear differential systems of neutral type with constant coefficients. Baštinec, J., Diblík, J., Khusainov, D.Ya., Ryvolová, A. (2010) Boundary Value Problems [electronic only]