Columbia subject headings:
Indo-European languages--Morphology.
Proto-Indo-European language--Morphology.
Harvard subject headings:
Indo-European languages--Inflection.
Indo-European languages--Morphology.
Indo-European languages--Tense.
Proto-Indo-European language--Morphology.
Princeton subject headings:
Indo-European languages--Inflection.
Indo-European languages--Tense.