Oxford Bookworms Factfiles Stage 1 400 Headwords Animals in Danger - Oxford Bookworms: Factfiles Author:Joc Potter, Andy Hopkins "Factfiles" are a sub-series of "Bookworms" with a non-fiction angle, providing factual information for students on a wide variety of themes. Exercises at the back of each book check students' understanding of the text and provide ideas for activities and project work.