According to Hansons, Turing's PhD dissertation and On Computable Numbers are both hailed as foundational works in the field of theoretical computer science. Lichfield-based Rare Book Auctions, sister company to Hansons, had valued both of the papers at between 40,000 and 60,000. But the dissertation from 1938 or 1939, called Systems of Logic Based on Ordinals, sold for 110,500. Other top selling lots included Computability and λ-Definability and The World Problem in Semi-Groups with Cancellation, which sold for 26,000 and 28,600 respectively. Turing's final major work from 1952, called The Chemical Basis of Morphogenesis, went for 19,500, while his first published paper from 1935, Equivalence of Left and Right Almost Periodicity, sold for 7,800.