Cannot install TDE trinity in Stretch box

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 In a box the hard drives of which had never been used, I installed a basic stretch, leaving me at the end only with the command line for any further packages installations. I the did the following: all these commands were run as root. Since I wanted to install TDE only -- no other DEs -- I ran command "apt-get x-window-system". When that was done I was able to run successfully startx. I added to /etc/sources.list the following two lines: deb http://mirror.xcer.cz/trinity-sb stretch deps-r14 main-r14 deb-src http://mirror.xcer.cz/trinity-sb stretch deps-r14 main-r14 I then ran successfully: sudo apt-key adv --keyserver keys.gnupg.net --recv-key A04BE668 and then "apt-get update && apt-get upgrade" successfully. When next I ran "apt-get install tde-trinity" the following was returned. Reading package lists... done Reading dependency tree Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not been created or been move out of Incoming. The following information may help to resolve the situation: The following packages have unmet dependencies: tde-trinity: Depends: tde-core-trinity (>= 4:14.0.0~) but it is not going to be installed. tde-trinity: Depends: tdegraphics-trinity (>= 4:14.0.0~) but it is not going to be installed. E: Unable to correct problems; you have broken packages. Running "aptitude install tde-trinity returns a similar message. I would appreciate it greatly if someone could tell me what all the foregoing means and what to do now to install the TDE. Regards, Ken Heard