This book seems to be content grandfathered in since a 1975 course and thus will likely have lots of obsolete material, despite being revised and compiled into

This book seems to be content grandfathered in since a 1975 course and thus will likely have lots of obsolete material, despite being revised and compiled into newer editions as the most major change was likely 1995 as it says in the below quote, which would likely explain the pre-1996 "Einfluß" and "Zusammenfluß" spelling. There was a 3rd edition in 2001 but they probably didn't manage to get to the issue. It is now a "open textbook was launched publicly on 22 October 2014 and is revised continually" so I would imagine they would be very pleased to see your corrections. >The second edition of this textbook was published in 1995 at the University of Wisconsin-Madison, copyright Howard Martin, primarily edited by Sue Tyson. Earlier versions apparently date back at least to a University of Wisconsin-Extension Independent Study course guide titled “A Guide to Reading German” “revised and expanded” by Howard Martin and published in 1975.