Ding Weiyue. (1970). Positive Solutions of {Delta <em>u</em>}+<em>u</em>^{(<em>n</em>+2)/(<em>n</em>-2)}=0 on Contractible Domains.
            <i>Journal of Partial Differential Equations</i>. <i>2</i> (4).
            83-88.
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