and van der Meulen, S.G., "Informal Introduction to ALGOL 68", North-Holland, 1971* McGettrick, A.D., "ALGOL 68, A First and Second Course", Cambridge Univ.
and Walker, A.N., "Introductory ALGOL 68 Programming", Ellis Horwood/Wiley, 1979* McGettrick, A.D., "ALGOL 68, A First and Second Course", Cambridge Univ.