This series was initiated in 1987 and is intended as a book series on topics that could be used as text books for upper level undergraduate or especially graduate level courses. The series is also usually created by a single or only a few authors, although this is not a requirement. This series can often result from an expansion of a Short Course Notes book. Books in this series are not always fully peer reviewed but the proposal and early drafts are reviewed by the Special Publications Editors or people they select. This series can optionally be produced in digital or print format (in soft or hard bound editions). The additional use of outside copy editors and type setters is also an option that may be used on this series but is not required depending on the state of the draft copies.