Hempl, George (1899). "The Origin of the Latin Letters G and Z". Transactions and Proceedings of the American Philological Association. 30: 24–41. doi:10.2307/282560. JSTOR282560.
Hempl, George (1899). "The Origin of the Latin Letters G and Z". Transactions and Proceedings of the American Philological Association. 30: 24–41. doi:10.2307/282560. JSTOR282560.