“…(Waters Received England and Wales, 1950and Roullston, 1969Charles, Cohen, Kass, and Richman 1970). In Great Britain, Thin and Michael (1970) found none, Rees and HIamlett (1972) foulnd 0s6 per cent., Cassie and Stevenson (1973) found 0s2 per cent., and Silverstone, Snodgrass, and Wigfield (1974) found none.…”