Xu, Chungen Some properties of non-positively curved metric spaces. (English) Zbl 0933.46004 J. Math., Wuhan Univ. 19, No. 1, 79-84 (1999). MSC: 46A19 46B20 47H10 47H09 PDFBibTeX XMLCite \textit{C. Xu}, J. Math., Wuhan Univ. 19, No. 1, 79--84 (1999; Zbl 0933.46004)
Cao, Wenchun Near smoothness, near convexity and drop properties and their applications. (Chinese. English summary) Zbl 0852.46012 J. Math., Wuhan Univ. 15, No. 2, 187-191 (1995). MSC: 46B20 46B10 PDFBibTeX XMLCite \textit{W. Cao}, J. Math., Wuhan Univ. 15, No. 2, 187--191 (1995; Zbl 0852.46012)