KOVALEV, Yu. G. On the criteria of transversality and disjointness of nonnegative selfadjoint extensions of nonnegative symmetric operators. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 70, n. 4, p. 495–505, 2018. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/1571. Acesso em: 5 dec. 2025.