1. B. Pontecorvo, Mesonium and anti-mesonium, Sov. Phys. JETP 6 (1957) 429 [Zh. Eksp. Teor. Fiz. 33 (1957) 549].
2. B. Pontecorvo, Inverse beta processes and nonconservation of lepton charge, Sov. Phys. JETP 7 (1958) 172 [Zh. Eksp. Teor. Fiz. 34 (1957) 247].
3. Z. Maki, M. Nakagawa, Y. Ohnuki and S. Sakata, A unified model for elementary particles, Prog. Theor. Phys. 23 (1960) 1174 [ INSPIRE ].
4. Z. Maki, M. Nakagawa and S. Sakata, Remarks on the unified model of elementary particles, Prog. Theor. Phys. 28 (1962) 870 [ INSPIRE ].
5. B. Pontecorvo, Neutrino experiments and the problem of conservation of leptonic charge, Sov. Phys. JETP 26 (1968) 984 [ INSPIRE ].