Vaskivska Г. О. . “GNOSEOLOGICAL VALUE TEXTBOOKS AS A MEANS OF REALIZATION AN INVARIANT AND VARIANT IS A COMPONENT OF THE CONTENT IN THE HIGH SCHOOL EDUCATION”. Problems of the Modern Textbook, no. 15, Dec. 2015, pp. 79-89, https://ipvid.org.ua/index.php/psp/article/view/449.