In your snippet call add:
If you want the raw value of a TV (eg the file location of an image reference) you need to include &includeTVs=`1`
If you want the processed value of a TV (eg an inline image) you need to include &processTVs=`1`
By the way - if you drag a snippet from the tree into your content (or any acceptable area) it will display the full propertyset for that snippet, which often saves time and helps you see other features.
Writer > E-consultant > MODx developer || Salesforce || modx 2.x || PHP 5.2.13 || MySQL client 5.0.86
Works very well! Thanks a lot!
Do you also know how to give the output-level-1 a certain style which is different to the output-level-2?
For example bold for level 1 and italic for level 2?
I think, thererfor I am! But what I am, and why...?
Thanks a lot for this hint. But as far as I understood the manual tplFirst serves for the first resource and not for the first level. Is this correct?
Ok, my mistake.

What do you exactly put in the word level in this case?
I think, thererfor I am! But what I am, and why...?
What do you mean by word level?
My goal is this:
Head (Resource Level 1)
Article 1 (Resource Output Level 2)
Article 2 (Resource Output Level 2)