Ron Willingham. The inner game of sellling. Free press.
Lua i Stíl Chicago (17ú heag.)Ron Willingham. The Inner Game of Sellling. Free press.
Lua MLA (9ú heag.)Ron Willingham. The Inner Game of Sellling. Free press.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.