Echo-cardiographic design of a multi-center investigation of free living elderly subjects - Gardin, JM; Wong, JD; Bommer, W; Klopfenstein, HS; Smith, VE; Tabatznik, G; Siscovick, D; Lobodzinski, S; Anton-Culver, H; Manolio, TA (J Am Soc Echocard, 1992)