411 REFERENCE · Wikibooks
Traditional Abacus and Bead Arithmetic/Contributors
Reference material by Wikibooks contributors. This retains its source identity and is not 411 news reporting.
User Jccsvq (discuss•contribs) has contributed the initial manuscript of this book by adapting some of his public domain (Creative Commons 0 1.0 Universal) writings from his personal website jccAbacus.