Finiding nodes filtered by attribute

All,
 
1)How would I do a match to find all <td> tags that don't have an attribute 
named class?
 
2)How would I do a match to find all <td> tags that don't have a class 
attribute equal to "a" or have no class attribute at all?
 
3)How would I do a math on all <td> tags that don't have any attributes?
 
Thanks,
Rechell
 

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