potkrepiti

1. (+ acc., with something) to support; to back up; to corroborate
   Svoju tvrdnju je potkrepio konkretnim podacima. — He backed up his claim with concrete data.
   Optužbe nisu potkrepljene nijednim dokazom. — The accusations are not supported by any evidence.
2. formal (potkrepiti se) to refresh oneself; to have a bite
   Posle duge šetnje potkrepili smo se supom. — After the long walk we refreshed ourselves with soup.

The means of support is in the instrumental: potkrepiti dokazima.