HELMER, R. G. (1991). Time Management For Engineers And Constructors Ray G. Helmer. American Society of Civil Engi.
Chicago-viite (17. p.)HELMER, Ray Gray. Time Management For Engineers And Constructors Ray G. Helmer. American Society of Civil Engi, 1991.
MLA-viite (8. p.)HELMER, Ray Gray. Time Management For Engineers And Constructors Ray G. Helmer. American Society of Civil Engi, 1991.
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