Or on the net, of course. The citation is (249 U.S. 47), and can be
found in many places (for example, on the FIndLaw Legal Resources site
at <http://www.findlaw.com/cgi-bin/getcase.pl?court=US&vol=249&invol=47>.
Though the court once held that the first amendment did not protect
commercial speech, that position was explicit overturned in 1976 by
Virginia State Board of Pharmacy v. Virginia Citizens Consumer Council,
Inc. (425 U.S. 748). The current controlling case regarding advertising
is Rubin v. Coors Brewing Co. 1995 (not yet published in U.S. Reports,
<http://www.findlaw.com/cgi-bin/getcase.pl?court=US&vol=000&invol=U10290>).
In that case, the court struck down as unconstitutional a BATF regulation
prohibiting Coors from listing the alcohol content of its beer its cans.