 The scheme can also be restricted. Equivalent to the assumption of 1-consistency, or \(\Sigma^{0}_1\)-soundness, for example, is the Reflection Principle restricted to \(\Sigma^{0}_1\)-sentences (i.e., the sentence \(A\) in the scheme is required to be a \(\Sigma^{0}_1\)-sentence.)  Or, it can be restricted to the universal \(\Pi^{0}_1\)-sentences; and so forth.