An experimental study of thinking, ”Arch. Psychol.“, 1924, 73;
   Problem solving in children and adults, ”J. o. Genet. Psychol.“, 1928, 35, p. 522–545;
   Toward a dinamic psychology of cognition, ”Psychol. Rev.“, 1945, 52, p. 1–22;
   The attainment of concepts, ”J. Psychol“, 1946, 35, p. 173–189, 191–223; 1947, 24, p. 93–138; 1948, 26; p. 193–216;
   Studying human thinking, in: ”Methods of Psychology (Ed. Andrews T.G.)“, 1948, p. 96–123.