Gang of Four: Design Patterns. Elements of Reusable Object-Oriented Software (1994; 2004 ed)

Book cover

Full reference I use in my notes:

[#gamma2004dp]: Erich Gamma, Richard Helm, Ralph Johnson,
  and John Vlissides (2004):  _Design Patterns. Elements of Reusable
  Object-Oriented Software_, Boston: Addison-Wesley.

Relevant Blog Posts

These are e.g. tagged with #design-pattern.