Perhaps you should try some spelling variations:
medical laboratories » clinical laboratories, national laboratories, hospital laboratories
virtual laboratories » virtual laboratory
federal laboratories » research laboratories, bell laboratories, general laboratory
medical laboratory » clinical laboratory

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: ((((((medical laboratories) OR (medical laboratory))) OR (virtual laboratories))) OR (((federal laboratories) OR (chemical laboratories)))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((((medical laboratories) OR (medical laboratory))) or (virtual laboratories))) or (((federal laboratories) or (chemical laboratories))))".
• Adding a wildcard symbol may retrieve word variants: ((((((medical laboratories) OR (medical laboratory))) or (virtual laboratories))) or (((federal laboratories) or (chemical laboratories))))*.