no. 2
The centroid and circumcentre of a plane convex set
Compositio Mathematica, Tome 21 (1969) no. 2, pp. 125-136. 
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     author = {Eggleston, H. G.},
     title = {The centroid and circumcentre of a plane convex set},
     journal = {Compositio Mathematica},
     pages = {125--136},
     publisher = {Wolters-Noordhoff Publishing},
     volume = {21},
     number = {2},
     year = {1969},
     mrnumber = {244859},
     zbl = {0179.27401},
     language = {en},
     url = {http://www.numdam.org/item/CM_1969__21_2_125_0/}
}
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Eggleston, H. G. The centroid and circumcentre of a plane convex set. Compositio Mathematica, Tome 21 (1969) no. 2, pp. 125-136. http://www.numdam.org/item/CM_1969__21_2_125_0/

H.G. Eggleston [1] An extremal problem concerning the centroid of a plane convex set. Colloquium on Convexity 1965. p 68. | Zbl