Perhaps you should try some spelling variations:
relational language » rational languages, regional language, functional language
national language » rational languages, functional language, natural language
plain language » latin language
2f grammar » 22 grammar, 26 grammar, 27 grammar
2 grammar » 2 grammars, _ grammar, a grammar
2f early » 21 early, ef early, f early
20 early » 10 early, 1820 early, 1720 early

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: %((plain language) OR (((relational language) OR (national language)))) %((2f grammar) OR (2 grammar)) %((2f early) OR (20 early)) works to 1800%22.
• The words AND, OR and NOT may confuse the search; try adding quotes: "%((plain language) or (((relational language) OR (national language)))) %((2f grammar) or (2 grammar)) %((2f early) or (20 early)) works to 1800%22".
• Adding a wildcard symbol may retrieve word variants: %((plain language) or (((relational language) OR (national language)))) %((2f grammar) or (2 grammar)) %((2f early) or (20 early)) works to 1800%22*.