The Celtic branch consists of two subgroups: Insular Celtic (Irish, Scots Gaelic, Welsh, Manx, Cornish and Breton) and Continental Celtic, now extinct (including Gaulish, Lepontic and Celtiberian).
  • Duval, P. M. (1985). Recueil des inscriptions gauloises. Paris: Editions du Centre national de la recherche scientifique.
    Olin Oversize DC30.G16 suppl.45 +

    A four-volume critical edition of the Gaulish inscriptions.

  • Evans, D. S. (1964). A grammar of Middle Welsh. Dublin: Dublin Institute for Advanced Studies.
    Olin PB2118.E929

    The standard reference grammar for Middle Welsh.

  • Jackson, K. H. (1953). Language and history in early Britain: A chronological survey of the Brittonic languages, first to twelfth century A. D. Edinburgh: University Press.
    Olin PB1028.J13 in room 501

    A massive work focusing on the evidence for the relative chronology of sound changes leading to the development of Welsh, Cornish and Breton.

  • Lewis, H., & Pedersen, H. (1961). A concise comparative Celtic grammar. G√∂ttingen: Vandenhoeck & Ruprecht.
    Olin PB1018.L67 1961

    The only comprehensive comparative Celtic grammar in English (out-of-date with regards to Continental Celtic).

  • McCone, K. (1996). Towards a relative chronology of ancient and medieval Celtic sound change. Maynooth: Department of Old Irish, St. Patrick's College.
    Olin PB1015.5.M357w 1996 in room 501

    A technical treatment of various issues in Celtic historical phonology.

  • Thurneysen, R. (1993). A grammar of Old Irish. Dublin: School of Celtic Studies, Dublin Institute for Advanced Studies.
    Olin PB1220.T54x 1993

    The standard comparative grammar of Irish.

  • Untermann, J., & Wodtko, D. S. (1975). Monumenta linguarum Hispanicarum. Wiesbaden: L. Reichert.
    Olin Oversize P1081.U61 M4 ++

    Contains a complete collection of Celtiberian inscriptions with vocabulary and commentary.

  • Vendryes, J., Bachellery, E., & Lambert, P. (1959). Lexique √©tymologique de l'irlandais ancien. Dublin: Dublin Institute for Advanced Studies.
    Olin PB1288.V45 in room 501

    A not-yet-complete etymological dictionary of Old Irish.