TY - JOUR T1 - Hypoellipticity of Nonlinear Second Order Partial Differential Equations AU - Xu Chaojiang JO - Journal of Partial Differential Equations VL - 1 SP - 85 EP - 95 PY - 1988 DA - 1988/01 SN - 1 DO - http://doi.org/ UR - https://global-sci.org/intro/article_detail/jpde/5856.html KW - AB -