The first medical record systems to employ EAV were the Regenstrief electronic medical record (the effort led by Clement MacDonald), William Stead and Ed Hammond's TMR (The Medical Record) system and the HELP Clinical Data Repository (CDR) created by Homer Warner's group at LDS Hospital, Salt Lake City, Utah. (The Regenstrief system actually used a Patient-Attribute-Timestamp-Value design: the use of the timestamp supported retrieval of values for a given patient/attribute in chronological order.) All these systems, developed in the 1970s, were released before commercial systems based on E.F. Codd's relational database model were available, though HELP was much later ported to a relational architecture and commercialized by the 3M corporation. (Note that while Codd's landmark paper was published in 1970, its heavily mathematical tone had the unfortunate effect of diminishing its accessibility among non-computer-science types and consequently delaying the model's acceptance in IT and software-vendor circles. The value of the subsequent contribution of Christopher J. Date, Codd's colleague at IBM, in translating these ideas into accessible language, accompanied by simple examples that illustrated their power, cannot be overestimated.)