Introduces 2 spellings for a vowel sound.

Book 1: ai, ay Book 2: ee, ea Book 3: oa, ow Book 4: ur, ir Book 5: e, ea Book 6: ow, ou Book 7: oo, ue Book 8: igh, i Book 9: 00, oul Book 10: or, aw Book 11: oy, oi Book 12: ar, a Book 13: air, are Book 14: ear, eer