Valery N. Shevchenko Nikolai Yu. Zolotykh Lower Bounds for the Complexity of Learning Half-Spaces with Membership Queries. 61-71 http://link.springer.de/link/service/series/0558/bibs/1501/15010061.htm 1998 conf/alt/1998 ALT db/conf/alt/alt1998.html#ShevchenkoZ98