Patente número 174.465 completa: http://www.freepatentsonline.com/0174465.pdf

Caderno de anotações de Bell: https://www.loc.gov/resource/magbell.25300201/?sp=47

Flood, J. E. (1976). Alexander Graham Bell and the invention of the telephone. Proceedings of the Institution of Electrical Engineers, 123(12), 1387. doi:10.1049/piee.1976.0281. Alexander Graham Bell and the invention of the telephone. Proceedings of the Institution of Electrical Engineers. IEEE. 1976. 10.1049/piee.1976.0281

How bell invented the telephone. (1947). Electrical Engineering, IEEE, 66(3), 232–236. doi:10.1109/ee.1947.6443414

A National Geographic Love Story: https://blog.nationalgeographic.org/2012/02/14/a-national-geographic-love-story/

McCain, [WIs1] John, Salter Mark. Hard Call: Great Decisions and the Extraordinary People Who Made Them. 2007.

Documentos da Família Alexander Graham Bell na Biblioteca do Congresso - Linha do Tempo: https://www.loc.gov/collections/alexander-graham-bell-papers/articles-and-essays/timeline/

Telefone e Telégrafo Múltiplo: https://www.loc.gov/collections/alexander-graham-bell-papers/articles-and-essays/telephone-and-multiple-telegraph/

Alexander Graham Bell: https://www.britannica.com/biography/Alexander-Graham-Bell

Quem realmente inventou o telefone? https://www.sciencefocus.com/science/who-really-invented-the-telephone/

Bell did not invent telephone, US rules: https://www.theguardian.com/world/2002/jun/17/humanities.internationaleducationnews

Como o telephone funciona? http://www.telcomhistory.org/vm/sciencePhonesWork.shtml

Joseph Henry A Life in Science: https://siarchives.si.edu/history/featured-topics/henry/joseph-henrys-life

Inventor of the Telegraph? https://siarchives.si.edu/sites/default/files/pdfs/jhpp/JHP_Inventor_of_the_Telegraph.pdf

A replica of ‘liquid transmitter’ telephone: https://artsandculture.google.com/asset/a-replica-of-%E2%80%98liquid-transmitter%E2%80%99-telephone/wgGf0Bh38GCERA

Anotações de Bell do transmissor Liquido:

https://www.loc.gov/resource/magbell.25300201/?sp=21

https://www.loc.gov/resource/magbell.25300201/?sp=22

Frequências naturais, harmônicos e sobretons: http://www.das.inpe.br/~alex/FisicadaMusica/fismus_freqnat.htm

Por que o Pe. Roberto Landell de Moura foi inovador? http://ebooks.pucrs.br/edipucrs/Ebooks/Web/978-85-397-0226-8/pages/v2.pdf

Empresa AT&T: https://pt.wikipedia.org/wiki/AT%26T

Nota musical: https://pt.wikipedia.org/wiki/Nota_musical

Tom: https://pt.wikipedia.org/wiki/Tom

Entre tantas outras pesquisas que não lembrei de anotar aqui. Acredito que com estas referências, já consigo dar uma direcionada em quem tiver interesse de pesquisar sobre o tema.