LSJ
ον, one with or against another, X. Eq. 4.3, Ach.Tat. 2.38.
congenial, π. καρπὸς πόπῳ prob. in Thphr. HP 2.2.8.
mutual, Phld. D. 3.14; correlative, Syrian. in Metaph. 34.23.
Liddell-Scott-Jones, Greek-English Lexicon (9th ed., 1940)
Pape
gegen einander, Theophr., zw.
Pape, Griechisch-deutsches Handwörterbuch (3. Aufl., 1914)