The Lead Masks (sources)

• "The Mystery of the Morro Do Vintem," by Charles Bowen, article in Flying Saucer Review, Vol. 13, No. 2, 1967. Pgs. 11-14. Available as PDF online at: https://www.reddit.com/r/UnresolvedMysteries/comments/3goalr/lead_masks_case_why_its_even_weirder_than_you/
• "No Easy Solution to the Morro Mystery," by Charles Bowen, article in Flying Saucer Review, Vol. 14, No. 4, 1968. Pgs. 36-37. Available as PDF online at: https://www.reddit.com/r/UnresolvedMysteries/comments/3goalr/lead_masks_case_why_its_even_weirder_than_you/
• "Follow Up on the Morro Do Vintem Mystery," by Gordon Creighton, article in Flying Saucer Review, Vol. 17, No. 4, July/August 1971. Pgs. 6-9. Available as PDF online at: https://www.reddit.com/r/UnresolvedMysteries/comments/3goalr/lead_masks_case_why_its_even_weirder_than_you/
• Confrontations, by Jacques Vallée, 1990 Ballantine Books, New York, USA. ISBN: 0-345-36453-8. Pgs. 4-15. Online in the Internet Archive Library: https://archive.org/details/confrontationssc00vall_0
• "Jacques Vallée," page in the Wikipedia website, viewed 2-28-2018. Online: https://en.wikipedia.org/wiki/Jacques_Vall%C3%A9e
• "O Caso das Mascaras de Chumbo," by Redação Vigília, page in the Portal Vigilia website, posted 1-5-1999, viewed 3-1-2018. Online [in Portuguese]: https://www.vigilia.com.br/o-caso-das-mascaras-de-chumbo-2/ - [Translated to English]: https://translate.google.com/translate?sl=auto&tl=en&js=y&prev=_t&hl=en&ie=UTF-8&u=https%3A%2F%2Fwww.vigilia.com.br%2Fo-caso-das-mascaras-de-chumbo-2%2F&edit-text=&act=url
• "O Caso Das Mascaras de Chumbo," by Paola Lucherini Covo, page in the INFA website, archived 4-21-2004, viewed 3-2-2018. Online [in Web Archive, Portuguese]: https://web.archive.org/web/20040421160028/http://www.infa.com.br/mascaras_de_chumbo.html - [Translated to English]: https://translate.google.com/translate?sl=auto&tl=en&js=y&prev=_t&hl=en&ie=UTF-8&u=https%3A%2F%2Fweb.archive.org%2Fweb%2F20040421160028%2Fhttp%3A%2F%2Fwww.infa.com.br%2Fmascaras_de_chumbo.html&edit-text=&act=url
• "The Lead Masks Case," page in the Wikipedia website, archived 11-28-2007, viewed 3-2-2018. Online [in Web Archive]: https://web.archive.org/web/20071128121132/https://en.wikipedia.org/wiki/Lead_Masks_Case

Memes

• "The Lead Masks Case," page in the me.me website, viewed 3-2-2018. Online: https://me.me/i/infa-on-august-17-1966-two-repairmen-miguel-jose-viana-9069781

Mentions & Repeaters

• "The Bizarre Lead Mask Deaths of 1966," by Stacy Conradt, article in the Mental Floss website, posted 10-22-2015, viewed 11-15-2016. Online: http://mentalfloss.com/article/70161/bizarre-lead-mask-deaths-1966