Complex sentence: Beg was first approached to write for the Encyclopaedia of Islam in 1973-over the years, he wrote 26 entries-mainly on occupational groups-making him one of the most prolific Muslim authors known to have written for this publication.
Split into simpler sentences: Beg was first approached to write for the Encyclopaedia of Islam in 1973. He went on to write 26 entries for it, mainly on occupational groups, making him one of the most prolific Muslim authors known to have written for this publication.