Another source of Luwian are the hieroglyphic seals which date from the 16th to the 7th centuries BC. Seals from the time of the Hittite empire are often digraphic, written in both cuneiform and hieroglyphics. However, the seals nearly always are limited to logograms. The absence of the syllabic symbols from the seals makes it impossible to determine the pronunciation of names and titles that appear on them, or even to make a certain attribution of the text to a specific language.