hip ▁at ▁the ▁University ▁of ▁California ▁at ▁Ber keley ▁in ▁ 1 9 4 0 . ▁On ▁August ▁ 2 0 , ▁ 1 9 4 0 , ▁he ▁married ▁L ora ine ▁G j ording . ▁The ▁couple ▁had ▁one ▁son ▁and ▁three ▁daughters . ▁ ▁V os per ' s ▁career ▁as ▁a ▁li br arian ▁included ▁director ships ▁at ▁the ▁W . A . ▁Clark ▁Memorial ▁Library ▁and ▁the ▁library ▁at ▁the ▁University ▁of ▁Kansas , ▁as ▁well ▁as ▁the ▁director ▁of ▁libraries ▁at ▁the ▁University ▁of ▁California , ▁Los ▁Angeles ▁( U CLA ) ▁where ▁he ▁began ▁in ▁ 1 9 6 1 . ▁ ▁In ▁ 1 9 7 3 , ▁V os per ▁retired ▁from ▁his ▁work ▁at ▁the ▁library ▁but ▁continued ▁to ▁teach ▁as ▁a ▁full - time ▁professor ▁at ▁U CLA ' s ▁school ▁of ▁library ▁science ▁until ▁ 1 9 8 3 , ▁followed ▁by ▁several ▁years ▁as ▁a ▁recall ▁professor . ▁ ▁Cont ribution s ▁to ▁the ▁library ▁profession ▁ ▁V os per ▁is ▁well ▁known ▁for ▁his ▁writ ings ▁on ▁the ▁field ▁of ▁li br ari ans hip ▁where ▁his ▁topics ▁included ▁the ▁importance ▁of ▁building ▁a ▁strong ▁book ▁collection ▁that ▁included ▁varied ▁topics ▁and ▁other ▁general ▁aspects ▁of ▁library ▁planning . ▁His ▁work ▁Ac quisition ▁Tr ends ▁in ▁American ▁L ibr aries , ▁written ▁in ▁ 1 9 5 5 , ▁str essed ▁that ▁book ▁ac quis itions ▁and ▁collection ▁development ▁were ▁important ▁aspects ▁of ▁any ▁library ▁and ▁should ▁not ▁be