One or more of the preceding sentences incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). "Ashlar". Encyclopædia Britannica. Vol. 2 (11th ed.). Cambridge University Press. p. 733. This also attests the alternative spellings ashler and ashelere.
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Wright, George R. H. (2000). Ancient Building Technology, Vol 1: Historical Background. Technology and Change in History. Leiden, The Netherlands: E. J. Brill. p. 100. ISBN978-90-04-09969-2. OCLC490715142.