Addresses of the authors

Postal mail
$\textstyle \parbox{.5\textwidth}{Wolfgang Kaspar\\ University of M\uml unste... ...steinstra\ss e 60\\ D-4400 M\uml unster\\ Federal Republic of Germany }$ $\textstyle \parbox{.5\textwidth}{H.$\!$-$\!$W$\!$.\ Kisker\\ University of M... ...steinstra\ss e 60\\ D-4400 M\uml unster\\ Federal Republic of Germany }$

E-mail
$\textstyle \parbox{.5\textwidth}{\tt urz86@dmswwu1a.bitnet}$ $\textstyle \parbox{.5\textwidth}{\tt urz10@dmswwu1a.bitnet}$

phone
$\textstyle \parbox{.5\textwidth}{49\ 2\,51\ 83\,24\,73}$ $\textstyle \parbox{.5\textwidth}{49\ 2\,51\ 83\,24\,67}$