The phrase "are valid only if" is correct and usable in written English.
It can be used to specify conditions under which something is considered valid or acceptable.
Example: "The results of the experiment are valid only if the procedures were followed precisely."
Alternatives: "are acceptable only if" or "are true only if".
TOEFL and IELTS scores are valid only if dated within two years of your program's application deadline.
TOEFL and IELTS scores are valid only if dated within two years of the program's application deadline.
The coupons are valid only if a certain number of people buy them, so would-be users must rally their friends, typically via Facebook or Twitter.
The opinion states, for example, that "to the extent that the legislature may enact laws regulating the electoral process, those laws are valid only if they impose no 'unreasonable or unnecessary' restraints on the right of suffrage" guaranteed by the state constitution.
To the extent that the Legislature may enact laws regulating the electoral process, those laws are valid only if they impose no "unreasonable or unnecessary" restraints on the right of suffrage: The declaration of rights expressly states that "all political power is inherent in the people".
And it goes on to say that to the extent the Legislature may enact laws regulating the electoral process, those laws are valid only if they impose no "unreasonable or unnecessary" restraints on the right of suffrage contained in the Constitution.
By conditional consecutive CID/ETD validation, we mean that a peptide is valid only if the particular peptide was identified from the exact same precursor by both CID and ETD but regardless of the score.
The Geneva Convention should be valid only if both parties agree to the conditions and requirements.
The California initiative would be valid only if all states processed their votes the same way.
The extrapolated results will be valid only if the gauss point coordinates are given in their undeformed state.
However, this ratio between the concentration and peak current is valid only if the electrochemically active area of the working electrode is constant in each electrochemical test.
