Perhaps you should try some spelling variations:
"put–hall parity" » "put–hall part", "put–hall patrick", "put–hall papists"
"put–cell parity" » "put–cell purity", "put–cell polarity", "put–cell part"
"put–call parity" » "put–all parity", "put–fall parity"

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: (((("put–call parity") OR ("put–hall parity"))) OR ("put–cell parity")).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"put–call parity\") OR (\"put–hall parity\"))) or (\"put–cell parity\"))".
• Removing quotes may allow a broader search: (((( put–call parity ) OR ( put–hall parity ))) or ( put–cell parity )).
• Adding a wildcard symbol may retrieve word variants: (((("put–call parity") OR ("put–hall parity"))) or ("put–cell parity"))*.