1. Aubry, S., Andre, G.: Analyticity breaking and Anderson localization in incommensurate lattices, Ann. Israel Phys. Soc.3, 133?164 (1980)
2. Bellissard, J.: Almost periodicity in solid state physics and C* algebras, Proceedings of the Harald Bohr Centenary conference on almost periodic functions, University of Copenhagen, to appear (1987)
3. Bellissard, J., Simon, B.: Cantor spectrum for the almost Mathieu potential, J. Funct. Anal.48, 408?419 (1982)
4. Butler, F., Brown, E.: Model calculations of magnetic band structure, Phys. Rev.166, 630?636 (1968)
5. Chambers, W.: Linear-network model for magnetic breakdown in two dimensions. Phys. Rev.140, A135-A143 (1965)