• On linearization of the Klein-Gordon equation by nontraditional methodsSaar, Rein; Loide, Rein-KarlEesti NSV Teaduste Akadeemia toimetised. Füüsika. Matemaatika = Известия Академии наук Эстонской ССР. Физика. Математика = Proceedings of Academy of Sciences of the Estonian SSR. Physics. Mathematics1983 / lk. 95-104 https://www.ester.ee/record=b1264310*est