Before revision:  And it is constructive in the sense that solutions to one of the inequality systems determine state and parameter vectors where the underlying mass action systems -- under explicitly stated genericity conditions -- undergo a saddle-node bifurcation  .
After revision:  And it is constructive in the sense that solutions to one of the inequality systems determine state and parameter vectors where the underlying mass action systems -- under explicitly stated genericity conditions -- undergo a saddle-node bifurcation occurs. Our conditions are applicable to general mass action networks involving at least one conservation relation, however, they are only sufficient (as infeasibility of linear inequalities does not exclude defective zero eigenvalues) .