00364nam a2200133 a 450000500170000002000150001708200200003210000190005224500570007126000480012830000230017670000170019970000140021620251203091927.0  a0521372267  a515.35,bD, Cho  aChow, Shui-Nee  aNormal forms and Bifurcation of planar vector fields  aCambridgebCambridge University Pressc1994  aviii,472p.c22 cm.  aLi, Chengzhi  aWang, Duo