Otakar Ševčík's for violin is a set of preparatory exercises for Jakob Dont's 24 Etudes or Caprices, Op. 35 . While it is less commonly found in a single file than his more famous bowing or technique schools, you can find the sheet music through several digital resources:
Sevcik - School Of Violin Technics, Op. 1, Book 1 ... - El Atril
: His exercises take a "surgical" approach, isolating technical problems like intonation, shifting, and finger dexterity so they can be practiced in "the shortest possible time".