Perhaps you should try some spelling variations:
2f politics » 2 politics, 20 politics, 21 politics
2.1 sources » 2.2 sources, 5.2 sources, 3.2 sources
20 sources » 10 sources, 0 sources, 22 sources
21 sources » 11 sources, 21 source, 21 resources

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: %((22new spain) OR (new spain)) %2f politics AND government %2f 18th century %((20 sources) OR (((((21 sources) OR (2.1 sources))) OR (2 sources))))%22.
• The words AND, OR and NOT may confuse the search; try adding quotes: "%((22new spain) or (new spain)) %2f politics and government %2f 18th century %((20 sources) or (((((21 sources) OR (2.1 sources))) or (2 sources))))%22".
• Adding a wildcard symbol may retrieve word variants: %((22new spain) or (new spain)) %2f politics and government %2f 18th century %((20 sources) or (((((21 sources) OR (2.1 sources))) or (2 sources))))%22*.