52 Pa. Code § 1.59
(b) The following number of copies of documents shall be served on other parties in a proceeding:
(1) Briefs:
The provisions of this § 1.59 amended under the Public Utility Code, 66 Pa.C.S. § § 501, 504—506, 523, 1301, 1501 and 1504.
The provisions of this § 1.59 amended April 28, 2006, effective April 29, 2006, 36 Pa.B. 2097; amended September 26, 2008, effective September 27, 2008, 38 Pa.B. 5303; amended January 10, 2014, effective January 11, 2014, 44 Pa.B. 249. Immediately preceding text appears at serial page (351345).
This section cited in 52 Pa. Code § 1.54 (relating to service by a party); and 52 Pa. Code § 5.502 (relating to filing and service of briefs).