This study has been extensively discussed by later scholars and several major criticisms have emerged. First, Durkheim took most of his data from earlier researchers, notably Adolph Wagner and Henry Morselli, who were much more careful in generalizing from their own data. Second, later researchers found that the Protestant–Catholic differences in suicide seemed to be limited to German-speaking Europe and thus may have always been the spurious reflection of other factors. Durkheim's study of suicide has been criticized as an example of the logical error termed the ecological fallacy. However, diverging views have contested whether Durkheim's work really contained an ecological fallacy. More recent authors such as Berk (2006) have also questioned the micro–macro relations underlying Durkheim's work. Some, such as Inkeles (1959), Johnson (1965), and Gibbs (1968), have claimed that Durkheim's only intent was to explain suicide "sociologically" within a holistic perspective, emphasizing that "he intended his theory to explain variation among social environments in the incidence of suicide, not the suicides of particular individuals."