Complex sentence: Very little is known about the Third Party Congress (also known as the Congress for Party Reconstruction) except that Pen Sovan was elected first secretary of the Central Committee and that the party then had between sixty-two and sixty-six regular members.
Split into simpler sentences: Very little is known about the Third Party Congress also known as the Congress for Party Reconstruction. Except that Pen Sovan was elected first secretary of the Central Committee and that the party had between sixty-two and sixty-six regular members.