Activity and discovery in mathematics.
Holland, William John.
Royal Society (Great Britain)
Royal Society (Great Britain).Royal Society's pamphlet Metric units in primary schools.
London : Hart-Davis Educational,
1970.
'Metric units in primary schools', by the Royal Society, originally published (B69-26817), London: Royal Society, 1969, classified at 372.7[1]
bibl. p. 29.
Mathematics.