in the popular Madrid daily ABC the usage ratio between “País Vasco” and “Provincias Vascongadas” was 1:1.4 in the 1910s (67 vs 94), 1.4:1 in the 1920s (295 vs 211) and 2.8:1 in the 1930s (until July 1, 1936, 635 vs 226), compare http://hemeroteca.abc.es/avanzada.stm
e.g. as "tres provincias forales", ABC 12.03.01, available here
for historic usage see Ramon Ortiz de Zarate, Biblioteca Vasco Navarra, Pamplona 1870, pp. 134-135, for contemporary usage see ABC 16.02.02, available here
Rubio Pobes 2003, p. 41, for example compare ABC 27.07.05, available here
in ABC the usage ratio between “provincias vascas” and “provincias vascongadas” was 1:4.7 in the 1910s, 1:3.2 in the 1920s and 1:2.2 in the 1930s (until July 1, 1936), compare search engine availeble here
in ABC the usage ratio between “País Vasco” and “Provincias Vascongadas” was 1:1.4 in the 1910s (67 vs 94), 1.4:1 in the 1920s (295 vs 211) and 2.8:1 in the 1930s (until July 1, 1936, 635 vs 226), compare here
e.g. in 1934 the ABC ratio between editorial usage (i.e. except commercials, official names etc.) of “Vascongadas” and “País Vasco” was ca 1:3, compare here
though it was seldom used, see ABC 29.06.58, available here
compare ABC 29.01.14, available here, or ABC 16.12.14, available here
bne.es
hemerotecadigital.bne.es
compare La Epoca 12.03.59, available here or Revista de archivos, bibliotecas y museos 01.02.97, available here, or s
for a sample see e.g. La Esperanza 01.09.1845, available here
Revista de Archivos, Bibliotecas y Museos 1 (1897), p. 495, available here
boe.es
compare BOE 252 (2012), available here; the usage appears to be actually an editorial negligence resulting form copy-pasting proper name of a company
books.google.com
e.g. José Canga Argüelles, Diccionario de Hacienda, vol. 2, Madrid 1834, p. 461-464 claimed that "este nombre llevan las de Navarra, Vizcaya, Álava y Guipúzcoa", compare here
congreso.es
"Araba, Biscay and Gipuzkoa, as well as Navarre, are members of the Autonomous Community of 'Euskal Herria'. They have a right to be". For the official text of the Basque version see here
for official text of the Basque-language document see here
the tension still persists, see the 2008 football incident here
uni-muenchen.de
mpra.ub.uni-muenchen.de
e.g. in the Real Decreto of 1847, see Juan Carlos Molero, Public Spending and Fiscal Federalism in Spain. Period 1984–1998, [in:] Munich Personal RePEc Archive 2008, pp. 42-3, available here
