http://books.google.com/books?id=IRbDaRDGpC4C&pg=PA71&lpg=PA71&dq=Heinrich+Rudolf+Wahlen&source=web&ots=hK55qut2f1&sig=EuodTER4uEkGutbuGIDRMpuey0U&hl=en&sa=X&oi=book_result&resnum=3&ct=result