Bertrand Russell. On the importance of logical form. Encyclopedia and unified science, International encyclopedia of unified science, vol. 1, no. 1, The University of Chicago Press, Chicago1938, pp. 39–41. - Rudolf Carnap. Logical foundation* of the unity of science. Encyclopedia and unified science, International encyclopedia of unified science, vol. 1, no. 1, The University of Chicago Press, Chicago1938, pp. 42–62.