Complex sentence: Until the 1930s, the records of the expedition remained dormant and it was only in 1945 that Emil Haury published, based on his dissertation, his monograph on Los Muertos, a site investigated in detail by the expedition.
Split into simpler sentences: Until the 1930s, the records of the expedition remained dormant. It was only in 1945 that Emil Haury published them through his dissertation, a monograph on Los Muertos, which was a site investigated in detail by the expedition.