Perhaps you should try some spelling variations:
firms transactions » firms transactional, free transactions, term transactions
transactions costs » transaction costs, transactions system
flows transport » goods transport, dots transport, flat transport
harold firms » held firms, harold adams, harold sir
held flows » heat flows, led flows

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( held flows transport services. ) or ( harold firms transactions costs. ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( held flows transport services. ) OR ( harold firms transactions costs. )).
• Adding a wildcard symbol may retrieve word variants: (( held flows transport services. ) or ( harold firms transactions costs. ))*.