References
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de Kerf, Joseph, The Common Mean and APL, Vector 11 3, Jan.1995
Graham, Ronald L., Donald E. Knuth, and Oren Patashnik, Concrete Mathematics: A Foundation for Computer Science, Addison-Wesley, 1988
Hui, Roger K.W., Some Uses of { and }, APL87, APL Quote-Quad, Volume 17, Number 4, 1987
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