To find cited references for an article in ACM Digital Library, do a simple or advanced search and in the detailed record, select the cited by tab to display articles that have cited this work.

Buchanan, George, David Bainbridge, Katherine J. Don, and Ian H. Witten. 2005. "A new framework for building digital library collections." Proceedings of the 5th ACM/IEEE-CS joint conference on Digital libraries, Denver, CO, USA.

Hover over the area below the Publication information (circled in red above), with the quotation symbol and the numbers. This area provides metrics data including total citations and total downloads of the article. 

To view more Biobliometrics and Citation information, click on the rising arrow button to the right of the Abstract (circled in red in screen shot below).

You can then click on the View Citations link to view the list of publications citing this particular paper.