S. Selberherr: "Device Modeling and Physics"; Physica Scripta (invited), T35 (1991), 293 - 298.
http://dx.doi.org/10.1088/0031-8949/1991/T35/057
http://www.iue.tuwien.ac.at/pdf/ib_1991/JB1991_Selberherr_1.pdf