1. Berkovitz Patent (1964)
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3. Thalen HJT, Rickards AF, Wittkampf FHM et al. (1981) Evoked response sensing (ERS as automatic control of the pacemaker output. Proceedings of the 2nd European symposium on cardiac pacing, Florence, pp 1229 1234
4. Preston TA, Bowers DL (1973) Report of a continuous threshold tracking system. In:Thalen HJT (ed) Cardiac Pacing. Van Gorcum, Amsterdam, p 295
5. Preston TA, Bowers DL (1974) The automatic threshold tracking pacemaker. Med Instrum (Baltimore) 8:322–325