The Case Law of the Boards of Appeal of the European Patent Office is a book, published by the European Patent Office (EPO), which summarizes the body of case law on the European Patent Convention developed by the Boards of Appeal of the EPO since the EPC entered into force at the end of the 1970s. Its ninth edition was published in September 2019. The book is also known as the "White Book", and it is the best-selling publication of the EPO. The White Book is published every three to four years. In the meantime, a special edition of the EPO Official Journal is issued each year summarizing the most recent case law of the boards of appeal.