Complex sentence: This assignment took Burr to archives in The Hague and London and he was also sent thousands of pages from the Venezuelan government, and in the end this effort occupied much of his time from 1896--1899.
Split into simpler sentences: This assignment took Burr to archives in The Hague and London. He was also sent thousands of pages from the Venezuelan government, and in the end, this effort occupied much of his time from 1896--1899.