DanylyukI. M., PetryshynR. I. and SamoilenkoA. M. (2007) “Averaging of initial-value and multipoint problems for oscillation systems with slowly varying frequencies and deviated argument”, Ukrains’kyi Matematychnyi Zhurnal, 59(3), pp. 412–430. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/3316 (Accessed: 22July2024).