Perhaps you should try some spelling variations:
voluntary hospitalization » involuntary hospitalization, involuntary hospitalisation, compulsory hospitalization
voluntary certification » voluntary participation, industry certification, voluntary sterilization

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: ((voluntary certification) OR (voluntary hospitalization)) / law AND legislation / slovakia.
• Adding a wildcard symbol may retrieve word variants: ((voluntary certification) or (voluntary hospitalization)) / law and legislation / slovakia*.