| 15.05.2008 | A mistake in the solution sketch for Exercise 1 on the first exercise sheet has been corrected. While the standard model of the ordered group of integer addition (without multiplication and 1) has as substructures just the one-element groupand isomorphic copies of itself, embedded via multiplication with a fixed natural number, as its substructures, these substructures are of distinct isomorphism types when multiplication is present as well! |
| 14.05.2008 | In the diagram depicting the ordinal numbers (in the excursion included in exercise sheet 6), the finite multiples of omega should have been labelled omega 2, omega 3 (and not in the opposite order). Ordinal multiplication is not commutative, and this is the right convention. Sorry. |
| 09.04.2008 | Exercise no.2 on sheet no.2 needs to be postponed, since we did not yet define logical equivalence and consequence. Sorry. |