Perhaps you should try some spelling variations:
courses practical » course practical, rouses practical, sources practical
astronomy surveys » astronomy survey, astronomy surveying, astronomy survives
astronomy sergey » astronomy survey, astronomy seven, astronomy large
more practical » some practical

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

• If you are trying to use Boolean operators, they must be ALL CAPS: the patrick ((courses practical) OR (more practical)) ((astronomy sergey) OR (astronomy surveys)).
• Adding a wildcard symbol may retrieve word variants: the patrick ((courses practical) or (more practical)) ((astronomy sergey) or (astronomy surveys))*.