题目：Viscosity solutions of fully nonlinear second-order elliptic partial differential equations 作者：H. Ishii* and P. L. Lions†
Journal of Differential Equations
Volume 83, Issue 1, January 1990, Pages 26-78
url
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WJ2-4CRM9F3-XX&_user=1021771&_coverDate=01%2F31%2F1990&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1345209890&_rerunOrigin=google&_acct=C000050170&_version=1&_urlVersion=0&_userid=1021771&md5=6f79dcb93177e4fa198c83ea7c7c22e3
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