A.Sh.Shaldanbayev, M.I.Akylbayev, A.A.Shaldanbayeva, и A.Zh.Beisebayeva, «ON THE SPECTRAL PROPERTIES OF A WAVE OPERATOR PERTURBED BY A LOWER-ORDER TERM», СФМН, вып. 4, сс. 22–29, авг. 2019.