 Equivalence results of these forms testify to the mathematical robustness of the class \(\mathbf{GR}\) and thereby also to that of the informal notion of effective computability itself. As we have seen, Gödel was originally led to the formulation of general recursiveness by attempting to analyze the background notion of recursive definition as a model of effective computation as inspired by the foundational developments of the late nineteenth and early twentieth  centuries.[17]  Further discussion of how the work of Church, Turing, and Post can be seen as providing independently motivated analyses of computability which also support Church’s Thesis can be found in Gandy (1980) and Sieg (1994, 1997, 2009).