In Lesson XI (p. 17), the vocabulary lists the principal parts of á¼€Î½Î±Î²Î±á½·Î½Ï‰ as:
á¼€Î½Î±Î²Î±á½·Î½Ï‰, (Î²Î±Î½-, Î²Î±-), á¼€Î½Î±Î²á½µÏƒÏ‰ (á¼€Î½Î±-Î²á½µÏƒÎ¿Î¼Î±Î¹), á¼€Î½á½³Î²Î·ÏƒÎ± (á¼€Î½á½³Î²Î·Î½)
I'm unclear about what's in the parentheses following the future and aorist forms. Are they future and aorist exceptions to the regular conjugations or rarer conjugations? In the exercises (53.1), á¼€Î½á½³Î²Î· is used as a 3rd person singular. This led me to wonder if they were using it to mean that á¼€Î½á½³Î²Î·- could be used as the augmented stem to which the same suffixes used in building the imperfect active indicative forms (I think these are referred to as the secondary tense endings?) are added.
Anyway, thanks in advance for any help and apologies if this sounds confused.