# Media credits for Unit 19 {#agc-media-credits-unit-19}

The single substantive media position in Lecture 19 retains its Commons identity and source licence. The two official PDFs are authority witnesses, not additional reader media positions.

1. **Twisted cubic curve** - [File:Twisted cubic curve.png](https://commons.wikimedia.org/wiki/File:Twisted_cubic_curve.png); creator/attribution: Claudio Rocchini; licence/rights status: [CC BY 3.0](https://creativecommons.org/licenses/by/3.0).

Rights note: the inline label on the lecture page is `CC-BY-SA-3.0`, whereas the frozen Commons description contains `{{self|GFDL|cc-by-3.0}}` and the Commons metadata offers [CC BY 3.0](https://creativecommons.org/licenses/by/3.0). The edition uses that Commons option, not the differing inline label.