Gibbs's retiring personality and intense focus on his work limited his accessibility to students. His principal protégé was Edwin Bidwell Wilson, who nonetheless explained that "except in the classroom I saw very little of Gibbs. He had a way, toward the end of the afternoon, of taking a stroll about the streets between his study in the old Sloane Laboratory and his home—a little exercise between work and dinner—and one might occasionally come across him at that time." Gibbs did supervise the doctoral thesis on mathematical economics written by Irving Fisher in 1891. After Gibbs's death, Fisher financed the publication of his "Collected Works". Another distinguished student was Lee De Forest, later a pioneer of radio technology.