Tributum

(Latin) an extra tax sometimes called for by the senate to be paid by Roman citizens; after 167 BCE, tributum was no longer allowed for Roman citizens, but it was still permitted that tributum could be sought from people in colonies.
Found on http://ablemedia.com/ctcweb/glossary/glossaryi.html

tributum

(from the article `taxation`) Early Roman forms of taxation included consumption taxes, customs duties, and certain `direct` taxes. The principal of these was the tributum, paid ...
Found on http://www.britannica.com/eb/a-z/t/78
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