sentence2: Ruby in a Nutshell ISBN 0-596-00214-9 The Ruby Programming Language ISBN 0-596-51617-7 Bill Venners (29 de setembro de 2003).
sentence1: Ruby in a Nutshell ISBN 0-596-00214-9 The Ruby Programming Language ISBN 0-596-51617-7 روبي (لغة برمجة).