1. Khalpakhchan, A.K., On Liquid Outflow through a Bottom Hole, Izv. Akad. Nauk Arm. SSR, 1948, vol. 1, no. 2, p. 91.
2. Polikovskii, V.I. and Perel’man, R.G., Voronkoobrazovanie v zhidkosti s otkrytoi poverkhnost’yu (Vortex Formation in a Liquid with an Open Surface), Moscow: Gosenergoizdat, 1959.
3. Belyaev, N.M. and Shandorov, G.G., Formation of a Nonrotating Cone in an Outflowing Liquid, Gidroaeromekhanika, Kharkov: Kharkov Univ., 1965, issue 2, p. 27.
4. Tokarev, V.E., Vortical Outflow of a Liquid from a Vessel, Izv. Vyssh. Uchebn. Zaved., Aviats. Tekh., 1967, no. 3, p. 85.
5. Ievlev, I.I., Vortex Formation in a Liquid Outflowing from a Cylindrical Vessel, Tr. Fizikotekh. Inst. Nizk. Temp. Akad. Nauk USSR, 1970, no. 1, p. 146.