or they reflect my own new insights in this area of Mathematics. New results are also discussed,

if related to the open questions in the book. The references in brackets correspond to the references in the book.

- Singular codes to compute some of the invariants discussed in Chapter 8 are available here "Singular Codes".

- (page 2) The first sum in Roberts' formula should be $\sum_{k\geq 3} n_k{k-1 \choose 2}$.

- (page 22) The equation for the $B_3$-arrangement from Example 2.4 becomes the equation $xyz(x-y)(x-z)(y-z)(x-y-z)(x-y+z)(x+y-z)=0$,

if we apply the linear coordinate change $X=-x+y+z$, $Y=x-y+z$, $Z=x+y-z$.

Hence the $B_3$-arrangement from Example 2.8 is the same as that in Example 2.4.

- (page 26) In the statement of Theorem 2.3, the Moebius function in the last sum should be $\mu(x,y)$ instead of $\mu(y,x)$.

- (page 27) For the notation $\A_X$ in the statement of Theorem 2.4, see Definition 2.13 on page 30.

- (page 33, line 3) Read $\pi(\A'',t)$ instead of $\chi(\A'',t)$.

- (page 163, line 1) Replace f by f '.