Pub.L. 100–568: The Berne Convention Implementation Act of 1988 (BCIA), 102 Stat. 2853, 2857. One of the changes introduced by the BCIA was to section 401, which governs copyright notices on published copies, specifying that notices "may be placed on" such copies; prior to the BCIA, the statute read that notices "shall be placed on all" such copies. An analogous change was made in section 402, dealing with copyright notices on phonorecords.
Garfinkle, Ann M; Fries, Janet; Lopez, Daniel; Possessky, Laura (1997). "Art conservation and the legal obligation to preserve artistic intent". JAIC 36 (2): 165–179.