I have imported a book and everything is OK aparently but I have those warnings on the admin logs admin. Is it important?

* warning: Cannot modify header information - headers already sent by (output started at /var/local/drupal/modules/contrib/bookimport/bookimport.module:189) in /var/local/drupal/includes/common.inc on line 266.
* warning: Cannot modify header information - headers already sent by (output started at /var/local/drupal/modules/contrib/bookimport/bookimport.module:237) in /var/local/drupal/includes/common.inc on line 266.

Excellent Module. Best Regards.