https://www.newscientist.com/article/mg21028133-600-unbreakable-beales-buried-treasure/
https://www.wired.com/2012/12/codes/
https://nakedsecurity.sophos.com/2013/03/01/the-top-10-unsolved-ciphertexts/
https://www.iacr.org/misc/china/
http://www.telegraph.co.uk/news/newstopics/howaboutthat/8293375/Top-10-uncracked-codes.html
https://en.wikipedia.org/wiki/Tamam_Shud_case
http://www.businessinsider.com/secret-d-day-code-found-on-a-dead-pigeon-has-historians-scrambling-for-ww-ii-codebreakers-2012-11
https://en.wikipedia.org/wiki/Linear_A
http://www.ancient-origins.net/unexplained-phenomena/mysterious-rongorongo-writing-easter-island-002242
https://en.wikipedia.org/wiki/Zodiac_Killer
https://en.wikipedia.org/wiki/Phaistos_Disc
https://en.wikipedia.org/wiki/Shugborough_inscription
http://cipherfoundation.org/modern-ciphers/chinese-gold-bar-ciphers/
http://www.dailytreat.net/view/no-one-can-decipher-these-mysterious-cryptic-codes/
https://en.wikipedia.org/wiki/Kryptos
https://en.wikipedia.org/wiki/D%27Agapeyeff_cipher
http://weburbanist.com/2010/05/31/cryptic-codes-11-legendary-uncracked-ciphers/