"most authoritative source" is a correct and usable phrase in written English.
You can use it to refer to a source of information that is considered to be the most reliable and trustworthy. For example, "The most authoritative source on this subject is the Encyclopedia Britannica."
"The Raising of Lazarus" is listed in Rodolfo Pallucchino's 1982 Tintoretto catalog, the most authoritative source on the Venetian artist.
And, according to Google, it's the most authoritative source on the internet on the "question" of whether or not the Holocaust actually happened.
Kassin read the U.S. Supreme Court's 1966 Miranda decision and found that it repeatedly cites the Reid Technique manual as the most authoritative source on American interrogation techniques.
Facebook is the most authoritative source on its own user numbers, and the firm will update investors on its performance for the March quarter on Wednesday.
As Peter Walker reported on Friday, this surprising, passing claim is strongly contradicted by the most authoritative source on blame in bike accidents.
"The Washington Post isn't the most authoritative source in Alabama," the lawyer said, "especially not in Coleman, or Gadsden, or Opp.
One of the most authoritative sources of information on cancer incidence, survival, and mortality is the Surveillance, Epidemiology and End Results (SEER) Program, sponsored by the U.S. National Cancer Institute.
In fact, the Sept. 11 attacks were an anomaly in an overall gradual decline in the number of terrorist attacks since the 1970s, according to the Global Terrorism Database, one of the most authoritative sources of terrorism statistics, which is maintained by a consortium of researchers and based at the University of Maryland.
They figure out which are the most authoritative sources for a given category and weight them accordingly.
A team of language researchers in Taipei led by doctoral candidate Ash Henson have gone over reams of paleographic research to find the most authoritative sources on the history and teaching of Chinese characters, and distilled that information into a format accessible even by beginners (a interactive demo is available online).
Most authoritative sources put the number of French civilians killed during World War II at nearly 300,000, with an estimated 75,000 of them killed by 550,000 tons of bombs dropped over France.
