. . . . "Periodic orbits"@en . "Periodic orbits" . . . . . . . . . . . . "Periodic Orbits : in Collaboration with" . . . . . "Periodic orbits by F.R. Moulton, in collaboration with Daniel Buchanan [and others]"@en . . . . . . . . "Periodic Orbits" . . . . "Periodic orbits, by F. R. Moulton" . . . . . . . . . . . . . "Orbits." . . "Orbites." . . . . "Többtestprobléma." . . "Égi mechanika." . .