Journal supplement [from Print source using APA 6th ed.]
Some journals produce supplementary issues, outside the normal pattern of issues for that volume. In this case, immediately after the volume number add in round brackets Suppl. and the supplement number.
Author, Initials. (year). Title of article. Title of journal, Volume number(Suppl. number of supplement), start and end page numbers of article.
Leftly, M. (2007, July 27). Blair, Brown and bling. Building, 272(30)(Suppl.), 6-7.
Citation in Text
Lefly (2007, p. 7) suggests that PFI schemes still haves some benefits for contractors ...