Pinata Winoto Gordon I. McCalla Julita Vassileva Non-Monotonic-Offers Bargaining Protocol. 1072-1079 2004 conf/atal/2004 AAMAS http://csdl.computer.org/comp/proceedings/aamas/2004/2092/03/20921072abs.htm db/conf/atal/aamas2004-3.html#WinotoMV04