(2002) International Encyclopaedia of Islamic Dynasties. New Delhi: Anmol Publications. ISBN 978-81-261-0403-1. “These Caliphs were the spiritual heads only. All temporal authority lay with the Mamluk Sultans. [...] In 1412 C.E. the Caliph Al Mustain captured temporal power as well, but he could not hold such power for more than six months. The Caliphs who followed him had to remain content as spiritual heads only.”.
