Perhaps you should try some spelling variations:
professional stories » professional series, professional studies, professional sports
profesional series » professional series, professional services, professional server
channel formation » channel estimation, channel modulation, channel function

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

• The words AND, OR and NOT may confuse the search; try adding quotes: "channel formation ((profesional series) OR (professional stories))".
• Adding a wildcard symbol may retrieve word variants: channel formation ((profesional series) OR (professional stories))*.