3Sandler PJ, Atkinson R, Murray AM. For four sixes. Am J Orthod Dentofacial Orthop,2000, 117:4]8-434.
4Daugaard-Jensen I.Extraction of first molars in discrepancy cases.Am J Orthos,1973,64:115-136.
5Hom BM. Turley PK. The effects of space closure of the mandibular first molar area in adults. Am J Orthod,1984,85:457-469.
6Williams R,Hosila FJ.The effect of different extraction sites upon incisor retaction.Am J Orthod,1976,69:388-410.
7Abu Aihaija ES,McSheny PF,Richardson A.A cephalometric study of the effect of extraction of lower first permanent molars.J Clin Pediatr Dent,2000,24:195-198.
8Seddon JL.Extraction of four first molars:a case for a general practitioner?J Orthod,2004,31:80-85.