Perhaps you should try some spelling variations:
communication concepts » communication circuits, communication congresses, communication channels
units dimensions » finite dimensions, its dimension, rims dimensions
concepts units » concepts unit, conceptual units, concepts finite
state spaces » state space
spaces » dspaces
space » dspace

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: communication concepts units dimensions ((((type spaces) or (shape space))) or (state spaces))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: communication concepts units dimensions ((((type spaces) OR (shape space))) OR (state spaces)).
• Adding a wildcard symbol may retrieve word variants: communication concepts units dimensions ((((type spaces) or (shape space))) or (state spaces))*.