Answer: aei

AnswerCrossword Clue
AEI.., O, U
AEIStart of a vowel recital
AEIStart of the vowels
AEIStart of a vowel sequence
AEIFirst three of five
AEIVowel sequence
AEIVowel trio
AEIScholarly org. that employs Robert Bork and Newt Gingrich
AEI"..., O, U, and sometimes Y"
AEISeries of letters before "O"
AEIVowel-sequence start
AEISeries of vowels before O
AEIOU opening