Wolfram, Walt; Schilling-Estes, Natalie, Dialectology and Linguistic Diffusion(PDF), Joseph, Brian D.; Janda, Richard D. (编), The Handbook of Historical Linguistics, Oxford: Blackwell: 713–735, 2003 [2022-01-29], (原始内容(PDF)存档于2021-11-10).
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Wolfram, Walt; Schilling-Estes, Natalie, Dialectology and Linguistic Diffusion(PDF), Joseph, Brian D.; Janda, Richard D. (编), The Handbook of Historical Linguistics, Oxford: Blackwell: 713–735, 2003 [2022-01-29], (原始内容(PDF)存档于2021-11-10).