 He engaged in much correspondence with Esperantists of other countries, did much Esperanto publicity, especially in The Hague, taught courses, and served as the secretary of the examinations committee from its establishment until the present.From 1910 on L. K. In latter years he worked only for Esperanto; as a novelist (of works originally in Esperanto), a translator and author of small booklets, Bulthuis has been one of the most enduring workers in Esperanto.Starting in 1907, when his translation from French of "Two Tickets" ("Du Biletoj") by Florian appeared, he published 35 books and brochures.