“Constructing a Basis from Systems of Eigenfunctions of One Not Strengthened Regular Boundary Value Problem”. ҚазҰУ Хабаршысы. Математика, механика, информатика сериясы, vol. 84, no. 1, June 2018, pp. 36-44, https://bm.kaznu.kz/index.php/kaznu/article/view/421.