Freivalds, A. (2014). Niebel's methods, standards, and work design 13th ed / Andris Freivalds dan Benjamin W. Niebel. Mc Graw-Hill.
Lua i Stíl Chicago (17ú heag.)Freivalds, Andris. Niebel's Methods, Standards, and Work Design 13th Ed / Andris Freivalds Dan Benjamin W. Niebel. Mc Graw-Hill, 2014.
Lua MLA (8ú heag.)Freivalds, Andris. Niebel's Methods, Standards, and Work Design 13th Ed / Andris Freivalds Dan Benjamin W. Niebel. Mc Graw-Hill, 2014.
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