Massive spin-0 and spin-1 wave equations. 1, Second-order equationsLoide, Rein-Karl1987 https://www.ester.ee/record=b1260527*est

Massive spin-0 and spin-1 wave equations. 2., First-order equationsLoide, Rein-Karl1987 https://www.ester.ee/record=b1260530*est

Some remarks on first order wave equationsLoide, Kadrin; Loide, Rein-Karl1977 https://www.ester.ee/record=b1274745*est