(HTM) Boettcher-refs.html
 (GIF) abstr1-41.gif
 (DOC) abstr1-41.pdf
 (TXT) abstr1-41.ps
 (HTM) pp1-41.html
 (DOC) pp1-41.pdf
 (TXT) pp1-41.ps
 (TXT) pp1-41.txt