SOLID (객체 지향 설계)
루비 (프로그래밍 언어) - 위키백과, 우리 모두의 백과사전
https://ko.wikipedia.org/wiki/%EB%A3%A8%EB%B9%84_(%ED%94%84%EB%A1%9C%EA%B7%B8%EB%9E%98%EB%B0%8D_%EC%96%B8%EC%96%B4)웨이백 머신 - 위키백과, 우리 모두의 백과사전
https://ko.wikipedia.org/wiki/%EC%9B%A8%EC%9D%B4%EB%B0%B1_%EB%A8%B8%EC%8B%A0SOLID Object-Oriented Design - Sandi Metz - GORUCO 2009
https://web.archive.org/web/20140329030135/http://www.confreaks.com/videos/240-goruco2009-solid-object-oriented-designhttp://www.confreaks.com/videos/240-goruco2009-solid-object-oriented-design
http://www.confreaks.com/videos/240-goruco2009-solid-object-oriented-designGetting a SOLID start. - Clean Coder
https://sites.google.com/site/unclebobconsultingllc/getting-a-solid-startArticleS.UncleBob.PrinciplesOfOod
http://butunclebob.com/ArticleS.UncleBob.PrinciplesOfOod