Sheldon, L. W. (1920). Twentieth century letter writer (1a. ed.). David Mc Kay, Publisher.
Dyfyniad Arddull ChicagoSheldon, L. W. Twentieth Century Letter Writer. 1a. ed. Filadelfia: David Mc Kay, Publisher, 1920.
Dyfyniad MLASheldon, L. W. Twentieth Century Letter Writer. 1a. ed. David Mc Kay, Publisher, 1920.
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