Hass, K. (1969). Creative salesmanship understanding essentials. George Press.
Lua i Stíl Chicago (17ú heag.)Hass, K. Creative Salesmanship Understanding Essentials. London: George Press, 1969.
Lua MLA (9ú heag.)Hass, K. Creative Salesmanship Understanding Essentials. George Press, 1969.
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