The 3rd paragraph of 35 U.S.C. 112 states that claims may be written in independent, dependent or multiple dependent form. Remember, an independent claim is one that stands alone. An independent claim does not depend on any other claim.

Dependent claims are those that do not stand on their own. These always refer back to another claim. Multiple dependent claims are dependent claims that refer back to more than one claim. Multiple dependent claims must refer back to the previous claims in the alternative form (i.e. using "or" as opposed to "and").