The category "<hour-not_initial_zero>" can be expressed as follows:
zero
oh
one
two
three
four
five
six
seven
eight
nine
ten
eleven
twelve
thirteen
fourteen
fifteen
sixteen
seventeen
eighteen
nineteen
twenty
one zero
one oh
one one
one two
one three
one four
one five
one six
one seven
one eight
one nine
two zero
twenty one
two one
twenty two
two two
twenty three
two three