APA (7th ed.) Citation

Usman, Z. (1990). Umar Bin Khattab Khalifah Kedua. Widjaya.

Chicago Style (17th ed.) Citation

Usman, Zuber. Umar Bin Khattab Khalifah Kedua. Widjaya, 1990.

MLA (8th ed.) Citation

Usman, Zuber. Umar Bin Khattab Khalifah Kedua. Widjaya, 1990.

Warning: These citations may not always be 100% accurate.