original_query: What were some important contributions made by Vitold Belevitch in the field of electrical network theory?
query: What were some important contributions made by Vitold Belevitch in the field of electrical network theory?
answer: Belevitch's important contributions to electrical network theory include introducing the scattering matrix (repartition matrix),  developing Belevitch's theorem (determining the constructibility of passive, lossless circuits from discrete elements), and writing a comprehensive textbook, Classical Network Theory, which unified the field using S parameters.