Modern Language Association
"MLA has turned to a style of documentation that is based on a general method that may be applied to every possible source, to many different types of writing. But since texts have become increasingly mobile, and the same document may be found in several different sources, following a set of fixed rules is no longer sufficient.
The current system is based on a few principles, rather than an extensive list of specific rules. While the handbook still gives examples of how to cite sources, it is organized according to the process of documentation, rather than by the sources themselves.
This process teaches writers a flexible method that is universally applicable. Once you are familiar with the method, you can use it to document any type of source, for any type of paper, in any field." – Purdue OWL