RDP 2009-02: Competition Between Payment Systems Equation (7)

\begin{array}{l} Ω_{i}^{m} = Ω_{i, ~ j}^{m} \cup Ω_{i, j}^{m} & , & Ω_{j}^{m} = Ω_{j, ~ i}^{m} \cup Ω_{i, j}^{m} \end{array}