Refer to conference proceedings published in hard copy in a collection in the same way as a chapter in a collected work.
Many organisations publish their conference presentations on their web pages.
Schlünz, G.I. & Barnard, E. 2013. A discourse model of affect for text-to-speech synthesis. Paper delivered at the 24th annual Symposium of the Pattern Recognition Association of South Africa, Pretoria. http://www.prasa.org/proceedings/2013/prasa2013-14.pdf Date of access: 15 Mar. 2019.
Text reference:
(Schlünz & Barnard, 2013).