Perhaps you should try some spelling variations:
electronic resources » electronic resource, electronic devices
electronic sources » electron sources, electronic resource, electron source
3.2 apache » 3.6 apache, 3.2.4 apache, 12 apache
2.2 apache » 2.0 apache, 2.5.2 apache, 5.2.2 apache
3a apache » a apache, 33 apache, 3.6 apache
3 apache » _ apache, 1 apache
5 apache » _ apache, 1 apache, 6 apache
4 apache » _ apache, 1 apache, 6 apache

Try widening your search to All Fields.

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: %22spark %((electronic sources) OR (electronic resources)) %((((3a apache) OR (((3.2 apache) OR (2.2 apache))))) OR (((((3 apache) OR (5 apache))) OR (4 apache)))) software foundation%29%22.
• The words AND, OR and NOT may confuse the search; try adding quotes: "%22spark %((electronic sources) or (electronic resources)) %((((3a apache) or (((3.2 apache) OR (2.2 apache))))) or (((((3 apache) or (5 apache))) or (4 apache)))) software foundation%29%22".
• Adding a wildcard symbol may retrieve word variants: %22spark %((electronic sources) or (electronic resources)) %((((3a apache) or (((3.2 apache) OR (2.2 apache))))) or (((((3 apache) or (5 apache))) or (4 apache)))) software foundation%29%22*.