There has been the failure to realize and … 1) if two people or groups of people … be common to both thesauri [private communication]; 2) if … index terms may be common to the two … [Borko, H. 1979, 7th Cranfield conf.]; 3) if two intermediaries search the same question on the … both searches [Cleverdon, C.W.1977 tech report]; 4) if two scientists or … question, the area of agreement may not exceed … [Cleverdon, C.W. 1970, tech report; Lesk ME and Salton G 1968 tech report]
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