1. Gorodetskii, V.V. and Kolisnyk, R.S., Differ. Uravn., 2007, vol. 43, no. 8, pp. 1086–1096.
2. Gelfand, I.M. and Shilov, G.E., Prostranstva osnovnykh i obobshchennykh funktsii (Spaces of Test and Generalized Functions), Moscow: Fizmatgiz, 1958.
3. Gelfand, I.M. and Shilov, G.E., Nekotorye voprosy teorii differentsial’nykh uravnenii (Some Questions in the Theory of Differential Equations), Moscow: Fizmatgiz, 1958.
4. Gelfand, I.M. and Shilov, G.E., Uspekhi Mat. Nauk, 1953, vol. 8, no. 6, pp. 3–54.