Theoretical literature about the subject exists see Heien and Wessells, 1990; Jabarin, 2005; Lazaridis, 2003; Perali and Chavas, 2000; Shonkwiler and Yen, 1999.
Existe literatura teórica referida a este tema véase Heien y Wessells, 1990; Jabarin, 2005; Lazaridis, 2003; Perali y Chavas, 2000; Shonkwiler y Yen, 1999.