Leskovec, J. and Horvitz, E.. Planetary-scale views on a large instant-messaging network. ACM New York, NY, USA, Year 2008.

Leskovec, Jure and Horvitz, Eric. Planetary-scale views on a large instant-messaging network. WWW '08: Proceeding of the 17th international conference on World Wide Web. 915--924, ACM, New York, NY, USA, Year 2008.