↑"Official Language", Concise Oxford Companion to the English Language, Ed. Tom McArthur, Oxford University Press, 1998.
↑Pueblo v. Tribunal Superior, 92 D.P.R. 596 (1965). Translation taken from the English text, 92 P.R.R. 580 (1965), p. 588-589. See also LOPEZ-BARALT NEGRON, "Pueblo v. Tribunal Superior: Español: Idioma del proceso judicial", 36 Revista Juridica de la Universidad de Puerto Rico. 396 (1967), and VIENTOS-GASTON, "Informe del Procurador General sobre el idioma", 36 Rev. Col. Ab. (P.R.) 843 (1975).
Writing Systems of the World: Alphabets, Syllabaries, Pictograms (1990), ISBN0-8048-1654-9 — lists official languages of the countries of the world, among other information.