Bill, S.(2007).Selling Results!: the innovative system for maximizing sales by helping your customers achieve their business goals .Singapura:KPG (Kepustakaan Populer Gramedia).
Gaya MLA
Stinnett, Bill."Selling Results!: the innovative system for maximizing sales by helping your customers achieve their business goals".Singapura:KPG (Kepustakaan Populer Gramedia),2007.Textbook.