books: 
  - "@isbn": 4-8443-1721-0
    title: "Rubyソースコード完全解説"
    authors: 
      - "青木峰郎"
      - "(監)まつもとゆきひろ"
  - title: "Ruby Way 〜Ruby道への招待〜"
    authors:
      - "Hal Fullton"
      - "(訳)やまだあきら"
      - "(訳)鵜飼文敏"
  - title: Ruby de XML
    authors:
      - "須藤功平"
