BARTUŠEK, Miroslav a John R. GRAEF. Limit-point/limit-circle results for super-linear damped equations. Abstr. Appl. Anal. Hindawi Pub. Corp., 2013, roč. 2013, Article ID784761, s. 1-10. ISSN 1085-3375. Dostupné z: https://dx.doi.org/10.1155/2013/784761.