 Complete the following phrase:  Trade was particularly important to the economy, as Bulgaria lay between the Byzantine Empire, Central Europe, the Rus and the steppes. Trade relations with the Byzantine Empire were regulated on a most favoured nation basis by treaties that included commercial clauses. The first such treaty was signed in 716 and provided that goods could only be imported or exported when embossed with a state seal. Goods without documents were to be confiscated for the state treasury. The Bulgarian merchants had a colony in Constantinople and paid favourable taxes. The relevance of international trade for Bulgaria was evident, as the country was willing to go to 