TY JOUR TI FREEDOM OF CONTRACT IN THE CONTEXT OF CONTRACTUAL REGULATION OF THE RIGHT TO UNILATERAL TERMINATION OF AN OBLIGATION KW freedom of contract KW unilateral refusal KW unmotivated refusal KW theory of effective breach KW balance of interests of the parties KW unfair contractual terms JO Advances in Law Studies AU Grigorev, O.I. PY 2026 IS 14 PB Publishing Center RIOR