Harutunyan, T. N. and Sahakyan, G. H. (2005) “ON A SPECTRAL PROBLEM FOR A SYSTEM OF PARTIAL DIFFERENTIAL EQUATIONS”, Proceedings of the YSU A: Physical and Mathematical Sciences. Yerevan, Armenia, 39(3 (208), pp. 40–46. doi: 10.46991/PYSU:A/2005.39.3.040.