@inproceedings{NZHP16, author = {M. Ni, Y. Zhang, W. Han and J. Pang}, title = {An empirical study on user access control in online social networks}, booktitle = {Proc.\ 21st ACM Symposium on Access Control Models and Technologies (SACMAT'16)}, publisher = {ACM Press}, year = {2016}, pages = {13-23} }