The book was originally written by Harold E. Harper, and later editions were co-authored with other experts in the field. The 31st edition is likely to have multiple authors, but I couldn't find specific information on the authors.
You're looking for a guide about Harper's Biochemistry 31st edition PDF. Here's some information:
Harper's Biochemistry is a well-known textbook in the field of biochemistry, first published in 1965. The 31st edition is one of the latest versions, providing comprehensive coverage of biochemical principles and their applications.