Perhaps you should try some spelling variations:
"formal language and automatic theory" » "formal language and automatic theorem", "formal language and automation theory", "formal language and axiomatic theory"
"formal languages and automata theory" » "formal languages and automated theory"

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: (("formal language and automatic theory") OR ("formal languages and automata theory")).
• Removing quotes may allow a broader search: (( formal language and automatic theory ) or ( formal languages and automata theory )).
• Adding a wildcard symbol may retrieve word variants: (("formal language and automatic theory") or ("formal languages and automata theory"))*.