49 CFR §172.304

1. (a)The marking required in this subpart—
   1. (1)Must be durable, in English and printed on or affixed to the surface of a package or on a label, tag, or sign.
   2. (2)Must be displayed on a background of sharply contrasting color;
   3. (3)Must be unobscured by labels or attachments; and
   4. (4)Must be located away from any other marking (such as advertising) that could substantially reduce its effectiveness.
2. (b)[Reserved]