"were attested" is a correct and usable phrase in written English.
It is typically used in a sentence to indicate that something has been confirmed, verified, or witnessed by someone. Example: The authenticity of the ancient artifact was confirmed by the experts, as it's age and origin were attested by several historical records.
Knox's "Truth", "Integrity" and "Credit" were attested to in statements from the very credit-worthy Christopher Wren and the Governor, Deputy-Governor and 24 named members of the Court of Committees of the East India Company, who included a fair sprinkling of baronets and knights.
When he was a youngster, his musical idols were trumpeters -- his cousin Theodore (Cuban) Bennett, who never recorded but whose advanced musical ideas were attested to by many musicians, and Bubber Miley, a star of Duke Ellington's orchestra in the late 1920's who lived around the corner.
The faults filtering and the improvement of the crystalline quality were attested by transmission electron microscopy and low temperature photoluminescence.
However, a series of impurities were attested with CuS if reaction temperature was not elevated high enough for their decompositions.
However, a series of impurities were attested with CuS if reaction temperature was not elevated high enough for the additional crystallite phase decomposition.
The functionalities of the method were attested and its analytical conditions, enhanced by using 22% of ACN and 6 min in the sample load step.
Trade with Syria and Palestine is attested by scenes of ships carrying foreign peoples.
The electric quality of his personality has been attested by his contemporaries.
By Vespasian's reign (69 79) organized companies (societates) of prospectors are attested.
Phrygia's relations with Assyria are attested to by Assyrian documents.
But, fanciful as it sounds, sperm-squeezing is attested to by another source.
