Source

• The J2EE 1.3 Tutorial (html
• The J2EE 1.4 Tutorial (html, pdf)
• The JavaEE 5 Tutorial (html, pdf)
• The JavaEE 6 Tutorial (html, pdf)
• The JavaEE 7 Tutorial (html, pdf)

Additional Sources

• Mastering EJB, Ed Roman (download free pdf)
• EJB Design Patterns, Floyd Marinescu (download free pdf, download source code)
• J2EE 1.3 API Documentation (html)
• J2EE 1.4 API Documentation (html)
• JavaEE 5 API Documentation (html)
• JavaEE 6 API Documentation (html)
• JavaEE 7 API Documentation (html)