On June 17, 1970, he formed a professional corporation, Sheldon Oliver Zisook Professional Corporation. The Commission commenced an investigation of Zisook in late 1979. A subpoena duces tecum was issued commanding the respondent to appear before the administrator of the Commission and to produce all files and documents in his possession relating to his representation of certain named clients. The subpoena also commanded Zisook to appear and give evidence.