BARTUŠEK, Miroslav,
Zuzana DOŠLÁ, Mariella CECCHI and Mauro MARINI. Fourth-order differential equation with deviating argument.
Abstract and Applied Analysis. USA: Hindawi Publishing Corporation, 2012, vol. 2012, ID 185242, p. 1-17. ISSN 1085-3375. Available from: https://dx.doi.org/10.1155/2012/185242.