The phrase "assiduously checking" is correct and usable in written English.
It can be used to describe someone who is diligently and persistently examining or verifying something.
Example: "The researcher was assiduously checking the data to ensure its accuracy before publication."
Alternatives: "diligently verifying" or "meticulously reviewing".
Black has used the considerable work on eugenics, assiduously checking sources, including my own, and drawn on original published and archival materials in the United States and Europe, collecting some 50,000 documents, he tells us, with the aid of numerous volunteers working in several dozen repositories.
Jack Loftus, the corporate spokesman for Nielsen, said the ratings company had assiduously checked its data and was confident the numbers were accurate.
I learned later that being shortchanged in Cuba is almost routine, and Cubans assiduously check the bill and their change.
By comparison, in 2007, the year before airlines began assiduously charging extra fees for checked bags and other services, that revenue was just $915.2 million.
It is to be examined assiduously — schools phoned, experience confirmed, references checked — by a fastidious professional.
You think newspaper journalists don't check their facts as assiduously as in the Old Days?
— The Relevant Organs (@relevantorgans) November 1, 2012 Chinese citizens from outside Beijing — especially those coming to the capital to present legal grievances or petitions — also are being checked and turned away more assiduously during the congress period.
But those materials, which are tracked just as assiduously as the steel is, first go by barge to the Fresh Kills landfill as a part of the "mixed debris" that investigators carefully check for crime evidence and personal effects.
Check, check, check, check.
Check, check, check, check, check, check, check.
Check, check, check, check, check.
