- Norm (mathematics) - Wikipedia
- Norm -- From MathWorld
- L1-Norm -- From MathWorld
- L2-Norm -- From MathWorld

"In linear algebra, functional analysis and related areas of mathematics, a **norm** is a function which assigns a positive *length* or *size* to all vectors in a vector space, other than the zero vector."

Wikipedia (2006)

"The norm of a mathematical object is a quantity that in some (possibly abstract) sense describes the length, size, or extent of the object."

MathWorld (2006)