Usefulness of approximate entropy for studying heart rate variability in Chagas' and arterial hypertension diseases during head-up postural test - Murta Júnior, Luiz Otávio; Nakazato, Kátia Cristiane; Crescêncio, Júlio César; Kozuki, Renata Torres; Maciel, Benedito Carlos; Gallo Júnior, Lourenço (Experimental Chaos Conference n(9, 2006)