He remains best known for his work as editor of the first edition (1913–38) of the standard encyclopedic reference work on Islam, the Encyclopaedia of Islam.
Theodoor de Booy | Vereniging Martijn | Theodoor Hendrik van de Velde | ''The Card Players'', 17th-century painting by Theodoor Rombouts | Jan Pieter Theodoor Huydecoper |