Satoshi Takahashi Tokuro Matsuo An Approach to Efficient Trading Model of Hybrid Traders Based on Volume Discount. 45-54 2008 New Challenges in Applied Intelligence Technologies http://dx.doi.org/10.1007/978-3-540-79355-7_5 series/sci/2008-134 db/series/sci/sci134.html#TakahashiM08