no. 1
On pinched manifolds with fundamental group 𝐙 2
Compositio Mathematica, Tome 27 (1973) no. 1, pp. 49-61 
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     author = {Grove, Karsten and Karcher, Hermann},
     title = {On pinched manifolds with fundamental group $\mathbf {Z}_2$},
     journal = {Compositio Mathematica},
     pages = {49--61},
     year = {1973},
     publisher = {Noordhoff International Publishing},
     volume = {27},
     number = {1},
     mrnumber = {334244},
     zbl = {0266.53032},
     language = {en},
     url = {https://www.numdam.org/item/CM_1973__27_1_49_0/}
}
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Grove, Karsten; Karcher, Hermann. On pinched manifolds with fundamental group $\mathbf {Z}_2$. Compositio Mathematica, Tome 27 (1973) no. 1, pp. 49-61. https://www.numdam.org/item/CM_1973__27_1_49_0/

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