Perhaps you should try some spelling variations:
practical astronomy » nautical astronomy, optical astronomy, positional astronomy
astronomy surveys » astronomy survey, astronomy surveying, astronomy survives
patrick drops » patrick debois, patrick dr, patrick arens
patrick brown » patrick browne, patrick barron, patrick bond

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: "the ((patrick drops) OR (patrick brown)) practical astronomy surveys".
• Adding a wildcard symbol may retrieve word variants: the ((patrick drops) OR (patrick brown)) practical astronomy surveys*.