@book{12136,
	author = {Symposium on Theoretical Approaches to Non Numerical Problem Solving, Case Western Reserve University, Ohio, Nov. 19-20, 1968 and Banerji, R. B. ; ed.},
	title = {Theoretical approaches to non numerical problem solving},
	publisher = {Springer-Verlag,},
	year = {1970},
	address = {Berlin:}
}