Perhaps you should try some spelling variations:
"pell's equation" » "pell equation"
"pol's equation" » "pole equation", "pol's equation2.8", "noll's equations"
"pulse equation" » "pulsar equation", "false equation", "phase equation"

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: (((((("pol's equation") OR ("pulse equation"))) OR ("pol equation"))) OR ("pell's equation")).
• Removing quotes may allow a broader search: (((((( pol's equation ) or ( pulse equation ))) or ( pol equation ))) or ( pell's equation )).
• Adding a wildcard symbol may retrieve word variants: (((((("pol's equation") or ("pulse equation"))) or ("pol equation"))) or ("pell's equation"))*.