By Open University Course Team
By Sterling, Mary Jane
By Bethell, George
By Forster, Jack, Wardle, M.E.
By Shasha, Dennis E.
By Lindsay, Sarah
By Stanczyk, Stefan, Champion, Bob, Leyton, Richard
By Lewin, Roger
By Waldrop, M.M.
By Gillian Rich
By Brian Seager, Mark Patmore
By Florence Campbell
By Fenna, Donald
By Singh, Simon
By Nuffield Foundation
By Fannon, Paul, Ward, Stephen
By Richardson, Peter
By Snape, Charles, Scott, Heather
By Julius, Edward H.
By Crowell, R. H., Fox
By Kent County Council
By Cambridge University Press, School Mathematics Project