35 U.S.C. § 112 : US Code - Section 112: Specification

      The specification shall contain a written description of the
    invention, and of the manner and process of making and using it, in
    such full, clear, concise, and exact terms as to enable any person
    skilled in the art to which it pertains, or with which it is most
    nearly connected, to make and use the same, and shall set forth the
    best mode contemplated by the inventor of carrying out his
    invention.
      The specification shall conclude with one or more claims
    particularly pointing out and distinctly claiming the subject
    matter which the applicant regards as his invention.
      A claim may be written in independent or, if the nature of the
    case admits, in dependent or multiple dependent form.
      Subject to the following paragraph, a claim in dependent form
    shall contain a reference to a claim previously set forth and then
    specify a further limitation of the subject matter claimed. A claim
    in dependent form shall be construed to incorporate by reference
    all the limitations of the claim to which it refers.
      A claim in multiple dependent form shall contain a reference, in
    the alternative only, to more than one claim previously set forth
    and then specify a further limitation of the subject matter
    claimed. A multiple dependent claim shall not serve as a basis for
    any other multiple dependent claim. A multiple dependent claim
    shall be construed to incorporate by reference all the limitations
    of the particular claim in relation to which it is being
    considered.
      An element in a claim for a combination may be expressed as a
    means or step for performing a specified function without the
    recital of structure, material, or acts in support thereof, and
    such claim shall be construed to cover the corresponding structure,
    material, or acts described in the specification and equivalents
    thereof.