gospodariti - to manage, to rule, to govern, to master

Hrvatsko - Engleski - Englesko - Hrvratski poslovni rijecnik, M. Cvejic

IMO, "businessman" is too general in this context, because not every businessman is automatelically a Manager, who is to lead, i.e. manage business matters of a Society/Association.

Croatian term (edited): s pozornošću urednog i savjesnog gospodarstvenika

This expression doesn't apply to a single person involved in some business, but to a business as an entity.

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Note added at 1 day10 hrs (2007-09-25 19:42:58 GMT)
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U slucaju nedostatka jasnih, izricitih uputstava u pismenoj formi, Banka može izvršiti nalog za placanje ili uplatu u skladu sa svojom procjenom postupajuci pri tome sa paznjom dobrog privrednika.
In the absence of clear and explicit written instructions the Bank may transact payment or deposit orders as it finds appropriate while acting in line with the best business practices.