HELMER, R. G. (1991). Time Management For Engineers And Constructors Ray G. Helmer. American Society of Civil Engi.
Lua i Stíl Chicago (17ú heag.)HELMER, Ray Gray. Time Management For Engineers And Constructors Ray G. Helmer. American Society of Civil Engi, 1991.
Lua MLA (8ú heag.)HELMER, Ray Gray. Time Management For Engineers And Constructors Ray G. Helmer. American Society of Civil Engi, 1991.
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