A Companion to Asian Art and Architecture, par Rebecca M. Brown, Deborah S. Hutton p. 428-
jstor.org
A Note on the Allahabad Pillar of Aśoka, C. S. Krishnaswamy Rao Sahib and Amalananda Ghosh, The Journal of the Royal Asiatic Society of Great Britain and Ireland No. 4 (Oct., 1935), pp. 697-706 p.704
scribd.com
John Irwin, The true chronology of Ashokan Pillars [1]