Complex sentence: R. Spencer Oliver has been the secretary general of the Parliamentary Assembly of the Organization for Security and Co-operation in Europe since its inception, having been chosen as the Assembly's first general secretary by the Bureau in a meeting of the OSCE Parliamentary Assembly in October 1992.
Split into simpler sentences: R. Spencer Oliver has been the secretary general of the Parliamentary Assembly of the Organization for Security and Co-operation in Europe since its inception. He was chosen as the Assembly's first general secretary by the Bureau in a meeting of the OSCE Parliamentary Assembly in October 1992.