COVEY STEPHEN R. (1995). PRINCIPLE CENTRED LEADERSHIP. SIMON & SCHUSTER INC.
Lua i Stíl Chicago (17ú heag.)COVEY STEPHEN R. PRINCIPLE CENTRED LEADERSHIP. LONDON: SIMON & SCHUSTER INC, 1995.
Lua MLA (9ú heag.)COVEY STEPHEN R. PRINCIPLE CENTRED LEADERSHIP. SIMON & SCHUSTER INC, 1995.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.