Lukac I. A covarinat form of the Maxwell's equations in four-dimensional spaces with an arbitrary signature / I. Lukac, 1991. - 21 p. - Текст : непосредственный.
Ellipsoidal basis for isotropic oscillator / W.Kallies,I.Lukac,G.S.Pogosyan,A.N.Sissakian, 1994. - 12 p. - Текст : непосредственный.