Irwin, John (1974). “'Aśokan' Pillars: A Reassessment of the Evidence-II: Structure”. 《The Burlington Magazine》 116 (861): 712–727. ISSN0007-6287. JSTOR877843.
The True Chronology of Aśokan Pillars, John Irwin, Artibus Asiae, Vol. 44, No. 4 (1983), pp. 247-265 [2]
Irwin, John (1974). “'Aśokan' Pillars: A Reassessment of the Evidence-II: Structure”. 《The Burlington Magazine》 116 (861): 712–727. ISSN0007-6287. JSTOR877843.