2. Bruxelles, Lamertin, 1923, in-8°, ca. 75 pp with a fine engraved frontispiece portrait by Louis Danse, sewn, orig. wrapper. Uncut, unopened copy. Published as an article of ca. 75 pp in the ''Annuaire de L'Académie Royale ses Sciences, des Lettres et des Beaux-Arts'', Year 89. Text in French, contains a bibliography of his works.