While writers such as Edouard Hugon, Réginald Garrigou-Lagrange, and Henri Grenier were maintaining the tradition of the manuals this did not mean that there was no variation or disagreement among thinkers about how best to formulate Thomism, especially in response to contemporary trends. Variation within the tradition of neo-scholastic Thomism is represented by Martin Grabmann (1875–1949), Amato Masnovo (1880–1955), Francesco Olgiati (1886–1962), and Antonin-Dalmace Sertillanges (1863–1948). Authors such as Étienne Gilson, Jacques Maritain, and Joseph Maréchal investigated alternative interpretations of Aquinas from the 1920s until the 1950s. Gilson and Maritain in particular taught and lectured throughout Europe and North America, influencing a generation of English-speaking Catholic philosophers.