The Riemann problem, complete integrability and arithmetic applications, Proc. Semin., France and USA 1979-1980, Lect. Notes Math. 925, 323-368 (1982).
The Riemann problem, complete integrability and arithmetic applications, Proc. Semin., France and USA 1979-1980, Lect. Notes Math. 925, 299-322 (1982).