Fradkin, DM (1967). «Existence of the Dynamic Symmetries O4 and SU3 for All Classical Central Potential Problems». Progress of Theoretical Physics37: 798–812. doi:10.1143/PTP.37.798. Bibcode: 1967PThPh..37..798F.
Fradkin, DM (1967). «Existence of the Dynamic Symmetries O4 and SU3 for All Classical Central Potential Problems». Progress of Theoretical Physics37: 798–812. doi:10.1143/PTP.37.798. Bibcode: 1967PThPh..37..798F.