(b) Two contiguous weak vowels with the accent on the second may or may not form a diphthong.
Ex. Si antes no juras que por ru^in falsía. Hermosilla. [Diphthong.]
Ex. Con sus mil rü|idos, p. 188, LXXIII, l. 19, [No diphthong.]
c. Two contiguous vowels after the accented syllable.
(1) Two contiguous strong vowels after the accented syllable naturally form a diphthong.
Ex. Tú, sombra aére^a que, cuantas veces, p. 170, XV, l. 7.
Diaeresis may be employed to dissolve the diphthong.
(2) If a strong vowel is followed by a weak vowel after the accented syllable, they form a diphthong, e.g. hablaba^is, amara^is.
This diphthong is easily dissolved.
(3) If a weak vowel is followed by a strong vowel after the accented syllable, they form a diphthong, e.g. histor^i^a, ans^i^a.