Johnston, M. W. (2008). Relationship SellingMark W. Johnston and Greg W. Mashall. McGraw-Hill.
Lua i Stíl Chicago (17ú heag.)Johnston, Mark W. Relationship SellingMark W. Johnston and Greg W. Mashall. McGraw-Hill, 2008.
Lua MLA (8ú heag.)Johnston, Mark W. Relationship SellingMark W. Johnston and Greg W. Mashall. McGraw-Hill, 2008.
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