This page says that standardization took place in year ~1700
So, where is it stated that English language has 26 letters and where are all letters defined?
This link https://en.wikipedia.org/wiki/History_of_the_Latin_alphabet says "By the 18th century, the standard Latin alphabet comprised the 26 letters we are familiar with today". But what is the source?
UPD:
The earliest document advised in answers to this question is
Samuel Johnson's Dictionary of the English Language, published in 1755, had the English alphabet codified.
Also, americans ITA-1 is dated by year 1929, see www.trafficways.org/ascii/ascii.pdf
UPD2: I want something like "there is a book in that library, which is first document which uses modern alphabet", something like Cawdry, Robert.; T. C.","1609", "A table alphabeticall". It is said, that it is available electronically for free under CC0 license, but I am unable to find the text.