It can of course also be used for non-numeric pages , for example `` f. 29 '' , `` A7 '' , `` back cover '' , etc. , and can also be used for non-paginated sources , e.g. `` 0:35:12 '' for a video source . Of course , it can also be used for non-numeric pages , for example : `` f. 29 '' , `` A7 '' , and `` back cover '' , etc. , and can also be used for non-paginated sources , e.g. , `` 0:35:12 '' for a video source .