Can't find package rt3.6-apache2


I’m trying to install RT 3.6 on my Ubuntu 6.06 (Dapper) system and have
followed instructions here:

Unfortunately, when I try:
apt-get install rt3.6-apache2
I receive the message:
Reading package lists… Done
Building dependency tree… Done
E: Couldn’t find package rt3.6-apache2

Seems it cannot find the package rt3.6-apache2.

Is there a reason it cannot be found? Where can I find it and how do I
install it?

Thanks very much for any help,