This comes from Morgunblaðið: Fé­lag tamn­inga­manna mæl­ir með tamn­ing­araðferðum sem byggja á gagn­kvæmri virðingu og trausti milli manns og hests (The horse trainers society advises training methods that are built upon mutual respect and trust between man and horse.) "hestur" is in indefinite genitive case here because of the preposition "milli"