a TOK 'E' uppercase in the style of Source Serif Pro is a serif typeface in the transitional style, designed to complement the Source Sans Pro family. The close companionship of Serif and Sans is achieved by a careful match of letter proportions and typographic color. Source Serif is loosely based on the work of Pierre Simon Fournier, and many idiosyncrasies typical to Fournier’s designs (like the bottom serif on the b or the middle serif on the w) are also found in Source Serif Pro.