In the mantis/doc folder are the following files:
.htaccess
ChangeLog
CREDITS
CUSTOMIZATION
INSTALL
LICENSE
In the INSTALL file, toward the end, you show the following:
-------------------------------------------------------------------------------
### Upgrading ###
-------------------------------------------------------------------------------
See the file: UPGRADING
-------------------------------------------------------------------------------
### Troubleshooting ###
-------------------------------------------------------------------------------
See TROUBLESHOOTING
As far as I can tell, the files UPGRADING & TROUBLESHOOTING do not exist and haven't existed for quite some time. Thanks!