
Much research and study of the baby head issues relies on past accounts and catalogues which record and describe the issues of that time. Descriptions of the literature sources are considered under the following groups:
Lopez (1890), Mencarini (1896), Galvez (1898), Cotter and Quinto (1897), Vives (1897), Harris (1898), Ceballos (1902), Circulado Filatelico Matritense (1902), Galvez (1932 to 1962), Catálogo EDIFIL (1964 to present), Catalogo Hevia (1948-1980?)
Schenkel (1900), Bartels, Palmer and Foster (1904), Hanciau..., Palmer (1912), Harradine (1996 check), Scott Catalogue (1868 to present), Stanley Gibbons Catalogue (1865 to present day)
French and German Language Catalogues
Friederich (1894), Belin (1898-1903), Minindo (1906), Yvert et Tellier Catalogue (1896 to present)
The Philatelic Record, Le Timbre-Poste, Gibbons Stamp Monthly Journal, The London Philatelist, Elizdale Stamp Journal, Philippine Journal of Philately, AFF Revista Dedicada al Fomento del la Filatelia, Philippine Philatelic Society Journal, Philippine Philatelic Journal
Gaceta de Manila, Gaceta de Madrid
Specialist Studies and Monograms
Peterson & Lewis (2000), Haerraiz (2016), Palmer (2023), Graus et al (1981), Laiz Castro (2006), Littrel (2010).
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