It would be good to add advanced search options which allow to filter the results.
The following functionalities should be added:
1. Possibility to display only Centers, Groups or Clients.
2. Possibility to display customers in particular state.
3. Possibility to display only customers created in given period of time.
Additional feedback from users:
concerning the search filters , filter by the ethnicity field would be great. Another one would be the "business activity" or country