Perhaps you should try some spelling variations:
profesional services » professional services, professional service, professional series
channel information » change information, changing information, channel interaction
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 information) OR (channel formation)) profesional services".
• Adding a wildcard symbol may retrieve word variants: ((channel information) OR (channel formation)) profesional services*.