JANYŠKA, Josef. A remark on natural quantum Lagrangians and natural generalized Schroedinger operators in Galilei quantum mechanics.
Supplemento ai Rendiconti del Circolo Matematico di Palermo,Serie II. Palermo, Itálie: Univerzita Palermo, 2001, roč. 66, č. 2, s. 117-128. ISSN 0009-725X.