Complex sentence: He recalled that during his first visit, the library had been a terrible mess, and no one had bothered to catalog it, so during his sabbatical Smith undertook the daunting task of cataloging the Mar Saba library.
Split into simpler sentences: He recalled that during his first visit, the library had been a terrible mess, and according to Smith no one had bothered to catalog it. BAR Agamemnon Tselikas Handwriting Analysis Report So, according to Smith, during his sabbatical Smith undertook the task of cataloging the Mar Saba library.