Perhaps you should try some spelling variations:
firms sanitation » firms organization, rural sanitation, site sanitation
from transaction » from transition, from translation, face transaction
transaction cost » transaction costs, transactions costs
harold from » harold bloom
head firms » held firms, lead firms, dead firms

You may be able to get more results by adjusting your search query.

• The words AND, OR and NOT may confuse the search; try adding quotes: "(( head firms sanitation services. ) OR ( harold from transaction cost. ))~".
• Adding a wildcard symbol may retrieve word variants: (( head firms sanitation services. ) OR ( harold from transaction cost. ))*.