 Theorem. (Diamond property for \(\triangleright_\textrm{sr}\)) If  \(M\triangleright_\textrm{sr}N\) and \(M\triangleright_\textrm{sr}P\) then there is a term \(Q\) such that both \(N\triangleright_\textrm{sr}Q\) and  \(P\triangleright_\textrm{sr}Q\). 