The Russian question particle li is such a clitic, e.g. Znaet li on ob ètom? [knows PTCL he about this] 'Does he know about this?'
These clitics were described in a classical article by Jacob Wackernagel (1892), and when interest in these clitics reawakened the 1970s, they became known as Wackernagel cltics.
- Wackernagel, Jacob. 1892. Über ein Gesetz der indogermanischen Wortstellung. Indogermanische Forschungen 1. 333-436.