. . . . . . . . . . . . "Bibliography"@en . "The clock problem (clock paradox) in relativity : theories, both pro and con, recorded in the literature : an annotated bibliography" . "The clock problem (clock paradox) in relativity : theories, both pro and con, recorded in the literature : an annotated bibliography"@en . . "The clock problem (clock paradox) in relativity"@en . . .