Significant % accident reduction : table of the minimum accidents required in the before period prior to a signifcant percentage accident reduction at the 5% level /
Hardy, M. F.
Hertfordshire (England).County Council.
[Hertfordshire] : Hertfordshire County Council,
1979.
Cover title.
"H.C.C. T.274/1."
"J.L.S.W./Jan. 1979."