1. ASTM, 1974, Annual Book of ASTM Standards, part 44, 730.
2. Bedford, R.E., Ma, C.K., Barber, C.R., Chandler, T.R., Quinn, T.J., Burns, G.W., Scroger, M.G., 1972 in Plumb (1972), part 3, 1585.
3. Berry, R.J., 1974, Metrol., 10, 145.
4. Berry, R.J., 1975 in Billing and Quinn (1975), 99.
5. Bezemer, J., 1974, Metrol., 10, 47.