Heller, R. (2004). Kinh doanh hiệu quả =: Selling successfully. Tp. HCM: Tổng hợp.
শিকাগো স্টাইলে সাইটেশনHeller, Robert. Kinh Doanh Hiệu Quả =: Selling Successfully. Tp. HCM: Tổng hợp, 2004.
এমএলএ সাইটেশনHeller, Robert. Kinh Doanh Hiệu Quả =: Selling Successfully. Tp. HCM: Tổng hợp, 2004.
সতর্কবাণী: সাইটেশন সবসময় 100% নির্ভুল হতে পারে না.