[1] HARVARD UNIV, CAMBRIDGE, MA 02138 USA
[2] MARYLAND MED RES INST, CTR COORDINATING, BALTIMORE, MD USA
[3] UNIV WASHINGTON, RADIOG CORE LAB, SEATTLE, WA 98195 USA
[4] YALE UNIV, RADIONUCLIDE CORE LAB, NEW HAVEN, CT 06520 USA
[5] UNIV VERMONT, COAGULAT CORE LAB, BURLINGTON, VT 05405 USA
[6] GEORGE WASHINGTON UNIV, ELECTROCARDIOG CORE LAB QUALIFYING CARDIOGRAMS, WASHINGTON, DC USA
[7] ST LOUIS UNIV, ELECTROCARDIOG CORE LAB EXERCISE ELECTROCARDIOGRAM, ST LOUIS, MO 63103 USA
[8] NHLBI, PROGRAM OFF, BETHESDA, MD 20892 USA
[9] NIH, CTR CLIN, PATHOL CORE LAB, BETHESDA, MD 20892 USA
[10] BROWN UNIV, PERCUTANEOUS TRANSLUMINAL CORONARY ANGIOPLASTY QUA, PROVIDENCE, RI 02912 USA
[11] VET ADM MED RES SERV, COOPERAT STUDIES PROGRAM, ALBUQUERQUE, NM USA