1. Opuscules mathématiques;d'Alembert,1761
2. Study of the motion of a string vibrating against an obstacle;Amerio;Rc. Mat. Applic.,1975
3. New results on the vibrating string with a continuous obstacle;Bamberger,1980
4. Almost periodic functions;Besicovitch,1932
5. A new approach to almost periodicity;Bochner;Proc. natn. Acad. Sci. U.S.A.,1962