[C++/.NET] When to use a reference

Q:
When should I return a reference from a function?

A: Basically there are two situations:

• The information being returned is a large enough object that returning a reference is more efficient than returning a copy. Just as it can be more efficient to pass large objects to functions by reference, it also can be more efficient to return large objects from functions by reference. Reference-return protocol eliminates the necessity of copying the object to a temporary location prior to returning.
  
• The type of the function must be an l-value. Reference-return types can also be useful when the function must evaluate to an l-value. Most overloaded operators fall into this category, particularly the assignment operator.
  

Quoted from: http://www.codeguru.com/forum/showthread.php?t=316925