00439nam a2200133Ia 4500082001800000100002000018245009700038260003200135300001000167650005900177650002700236650002200263650002000285  a025.432 PER-;  aPerreault, J.M. 0aTowards a theory for UDC: essays aimed at structural understanding and operation development  aLondonbClive bingleyc1969  a241p.  aClassification, Universal decimal - Study and teaching  aClassification - Books  aLibrary education  aLibrary science