The phrase "attested written" is correct and usable in written English.
It can be used in contexts where you want to refer to something that has been formally confirmed or verified in written form.
Example: "The attested written agreement between the parties serves as proof of their mutual understanding."
Alternatives: "verified document" or "authenticated writing".
Mongolian literature is well attested in written form from the 13th century but has earlier Mongolic precursors in the literature of the Khitan and other Xianbei peoples.
"As anyone who saw Ethel live will attest," Flinn writes, "she had an absolutely magnetic presence in front of a live audience.
As a scientist who performs complicated experiments for a living, I can attest that writing down exactly what I have done in minute detail is the only way that my experiments – sometimes lasting up to a month in duration – can ever be useful.
Paul Heggarty, a linguist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, questions Garrett's methods, arguing that, for example, linguists cannot be sure if the Latin attested to in written documents really was the direct ancestor of later Romance languages, rather than some dialect of Latin for which no record remains.
(iii) the witness attests that the written statement or transcript accurately reflects that witness' declaration and what the witness would say if examined.
It is one of the earliest attested examples of written Old English and one of the earliest recorded examples of sustained poetry in a Germanic language.
Old Persian, spoken until approximately the 3rd century bce, is attested by numerous inscriptions written in cuneiform, most notable of which is the great monument of Darius I at Bīsitūn, Iran.
By far the largest part of attested Old Iranian is written in the language now usually called Avestan, after the Avesta, the name given to the collection of works forming the scripture of the Zoroastrians.
The Mycenaeans were ultimately the first Greek-speaking people attested through historical sources, written records in the Linear B script, and through their literary echoes in the works of Homer, a few centuries later.
