Hidekazu Sakagami Tomonari Kamba Atsushi Sugiura Yoshiyuki Koseki Effective Personalization of Push-Type Systems - Visualizing Information Freshness. 53-63 1998 30 Computer Networks 1-7 db/journals/cn/cn30.html#SakagamiKSK98 http://dx.doi.org/10.1016/S0169-7552(98)00060-9