The phrase "an even more rigorous" is correct and usable in written English.
It can be used when comparing the level of rigor in two or more contexts, indicating that one is more rigorous than another.
Example: "The new study employs an even more rigorous methodology than the previous research."
Alternatives: "a significantly stricter" or "a considerably tougher".
Returning to Britain in 1942, Greville went to an even more rigorous education at St Paul's School, London.
He suggested Britain could bring in an even more rigorous immigration system than a points-based system.
Vice President Dick Cheney has an even more rigorous schedule, and the administration intends to send cabinet secretaries to help candidates, too.
Greatly influenced by Jasper Johns's flag paintings, Mr. Stella sought an even more rigorous logic between physical and visual by using parallel bands of black that either reiterate or run diagonally to the edges of the canvas.
To do this he used an even more rigorous version of the system, in which an employee must wave a security card and then step into a glass tube before submitting to the iris scanner.
GARMISCH-PARTENKIRCHEN, Germany — If the super-G on the exceedingly bumpy, shady and highly demanding Kandahar piste was any indication, the world's elite speed skiers are surely in for an even more rigorous test Saturday when the downhill is contested at the world ski championships.
Mr. Rehn also promised "a new round of even more rigorous and even more comprehensive bank stress tests," beginning in February.
Saints are the church's spiritual role models, chosen because they died for their faith, or lived for it in especially memorable ways, through a process that grew even more rigorous last month, when the Vatican issued stricter guidelines to the bishops who propose candidates.
"The policies that governed the foundation's activities during Hillary Clinton's tenure as secretary of state already went far beyond legal requirements," he said in a statement, "and yet the foundation submitted to even more rigorous standards when Clinton declared her candidacy for president, and is pledging to go even further if she wins".
Monks are expected to suffer with equanimity hardships imposed by the weather, geographic terrain, travel, or physical abuse; however, exceptions are allowed in emergencies, since a monk who survives a calamity can purify himself by confession and by practicing even more rigorous austerities.
And also to make the science even more rigorous.
