Added reference to function

doc/datasets/olivetti_faces.rst

@@ -8,7 +8,9 @@ The Olivetti faces dataset
 This dataset contains a set of face images taken between April 1992 and April
 1994 at AT&T Laboratories Cambridge. The website describing the original
 dataset is now defunct, but archived copies can be accessed through
-`the Internet Archive's Wayback Machine`_.
+`the Internet Archive's Wayback Machine`_. The `sklearn.datasets.fetch_olivetti_faces`
+function is the data fetching / caching function that downloads the data
+archive from AT&T.
 
 .. _the Internet Archive's Wayback Machine: http://wayback.archive.org/web/*/http://www.uk.research.att.com/facedatabase.html