Perhaps you should try some spelling variations:
"maximum principal" » "maximum principle", "maximum principles", "maximal principle"
"maximin principle" » "maximum principle", "maximum principles", "minimax principle"
"minimum principle" » "maximum principle", "maximum principles"

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: (((("maximum principal") OR ("maximin principle"))) OR ("minimum principle")).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"maximum principal\") OR (\"maximin principle\"))) or (\"minimum principle\"))".
• Removing quotes may allow a broader search: (((( maximum principal ) OR ( maximin principle ))) or ( minimum principle )).
• Adding a wildcard symbol may retrieve word variants: (((("maximum principal") OR ("maximin principle"))) or ("minimum principle"))*.