What does YEAR: NNff means in research papers? eg 1965: 47ff
"ff" stands for "and following" so in your case it is page 45 and following pages that are indicated. It should be used when no stop page can be given. The abbreviation comes from the latin for page foilum plur. folia. Originally one would write page 45f to indicate just the following page, i.e. "45-46". The two f's indicate more than one page so "45 and on".