Such arithmetic would have been essential as the islands became important trade centers. (sciencemag.org)
The Pastor of Zwichau: Zwickau, because of its strategic geographic location with Leipzig, belonged to Germany's most important trade centers. (religion-online.org)
After conquering the Etruscans during the third century A.D., the Romans established Florence as an important trading center. (jovinacooksitalian.com)