Andrew H. Frost and Charles A. M. Fennell, 1911 Encyclopædia Britannica, Volume 17… (1911)
“ From a perfect magic ring of n2 cells containing one number each, n2 distinct magic squares can be read off; as the four numbers round each intersection of a zonal circle and a transverse circle constitute corner numbers of a magic square. The shape of a magic ring gives it the function of an indefinite extension in all directions of each of the aforesaid n2 magic squares. ”
