Exercise on contracted verbs

[marcovlatinforum]

Hi Textkit. This semester has been tough going, but I'm now turning back for a while to my Greek books.

An exercise in Μελετήματα A asks me to identify form the list below all the contracted verbs.
The verb forms in the list are: φιλεῖ, φλέγει, βαδίζει, ἡσυχάζει, κάμνει, στενάζει, γεωργεῖ, χαίρει, φέρει, οἰκεῖ.

I know that a verb is said to be "contracted" if the ending of its stem is an α, an ε or a ι. I don't know at the moment how to recover the stem form a conjugated verb form: this exercise is meant to be done after the first chapter of the first volume of the Athenaze course, where even the -ω, -εις, ec. endings for the first singular present are still to be introduced.

My attempt: knowing a bit about accents, but without looking at the dictionary, I would say that the contracted verbs here are φιλεῖ, and οἰκεῖ (but I might better go refreshing my memory a bit).

[Barry Hofstetter]

One more... look at them carefully, all the contracts have one thing in common...

[marcovlatinforum]

Of course, I forgot γεωργεῖ!

all the contracts have one thing in common...

I thought it might be the circumflex, but in fact I wasn't quite sure.

Thank you.