Filter a table before join

Hi,

i need help for a cristal report with DATASETS and SQL.

I have a table with people and another with his anual readings. Both in a dataset.

Table PERSON:

     NUMPERSON

     NAME

Table READINGS

     NUMPERSON

     YEAR

     NUMBOOKS

How i can list the name of person who didn't read any book in the year indicated with a report parameter?

Thanks