faclair.com - Dictionary.
www.celtic-languages.org/Gaelic/Resources - Scottish Gaelic resources, courses, dictionaries, media, etc.
learngaelic.scot - Resources, videos, audio, dictionary, etc.
www.celtic-languages.org/Guide_to_Scottish_Gaelic_to_be,_the_linking_verbs:_substantive_bi,_tha_%26_the_copula_is - Guide to Scottish Gaelic 'to be', the linking verbs: substantive 'bi', 'tha' & the copula 'is'.
duome.eu/tips/en/gd/ - The grammar notes that were removed from the Duolingo Scottish Gaelic course.
The Principles of Gaelic Grammar, by Forbes (1848)
Kauderwelsch Schottisch-Gälisch Wort für Wort, by Klevenhaus (2015)
Etymological Dictionary of Scottish-Gaelic, by MacBain (1982)
Gaelic Language Practice, by Maciver (1980)
Teach Yourself Gaelic, by Mackinnon (1971)
A Pronouncing and Etymological Dictionary of the Gaelic Language, by Maclennan
The Gaelic-English Dictionary, by Mark (2003)
Scottish Gaelic in Three Months, by Ó Maolalaigh and MacAonghuis (1998)
Scottish Gaelic in Twelve Weeks, by Ó Maolalaigh and MacAonghuis (2008)
Teach Yourself Scottish Gaelic, by Robertson and Taylor (1993)
Colloquial Scottish Gaelic: The Complete Course for Beginners, by Spadaro and Graham (2001)
Essential English-Gaelic Dictionary, by Watson (2005)
Scottish Gaelic, in The Celtic Languages, 1st edition, by Gillies (1993)
Scottish Gaelic, in The Celtic Languages, 2nd edition, by Gillies (2009)
Scottish Gaelic Today - Social history and contemporary status, in The Celtic Languages, 1st edition, by MacKinnon (1993)
Scottish Gaelic Today - Social history and contemporary status, in The Celtic Languages, 2nd edition, by MacKinnon (2009)
Scottish Gaelic Dialects, by Robertson (1906)