汗牛充棟 [ㄏㄢˋ ㄋㄧㄡˊ ㄔㄨㄥ ㄉㄨㄥˋ; han4 niu2 chong1 dong4]
  lit. enough books to make a pack-ox sweat or to fill a house to the rafters (idiom); fig. many books
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  汗牛充棟
  かんぎゅうじゅうとう
  noun (common) (futsuumeishi)
  (having, there being) a great number of books
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