Algebra Learning
Edwards, E.L.,Jr. (ed.) (1990) Algebra for Everyone. National Council of Teachers of Mathematics: Reston, VA.  
[in HKUL] [in Learning Math]
Mason, J., Graham, A. & Johnston-Wilder, S. (2005) Developing Thinking in Algebra London, Open University & Paul Chapman Publishing
[in HKUL]
DfES (2004) Interacting with Mathematics in Key Stage 3, Constructing and Solving Linear Equations: Pre-course Reader.
which is an extract of Key Aspects of Teaching Algebra in Schools by J. Mason and R. Sutherland (UK: QCA, 2002)
Mason, J. (1991) Routes to, Roots of Algebra. Milton Keynes: Open University.
[in HKUL]

Algebra Applets in Wisweb, Freudenthal Institute