I think you're right to keep Deutsche Grammophon Literatur as a label, it looks as though it has its own Label Code
13542, which began to be used around 2005. Earlier releases under the Deutsche Grammophon Literatur brand seem to usually display the Deutsche Grammophon Label Code
Looking closely at Deutsche Grammophon Resonance I'm not sure I would regard it as a Series either. Looking at the guidelines (emphasis mine):
A series is a sequence of separate release groups, releases, recordings, works or events with a common theme. The theme is usually prominent in the branding of the entities in the series and the individual entities will often have been given a number indicating the position in the series.
What's the common theme? Looking at two releases on Resonance: this 1974 LP and this 1994 CD, it doesn't seem obvious to me that they're part of the same series. The branding is different and the catalogue numbers don't have a sequential relation. The 1994 release also lacks the standard Deutsche Grammophon logo (below) which is a problem if it's supposed be the new release label.
This might be an overly strict interpretation of the guideline, and I don't think it's wrong to describe Resonance as a series, the question I have is whether it's a legitimate Series Entity.