Rapid estimation of plasma theophylline concentrations.

12 year old and 19% of 18 year old Finns.'These differences may be related to the socioeconomic climate in the two countries when the studies were undertaken.The Finnish study was undertaken in Febru- ary 1983, when the percentage of unemployment was 6% (abstracts from the Finnish Embassy's annual statistical year book, 1984 (unpublished)), whereas unemployment in the United Kingdom in March 1984 was 13% and within the city of Nottingham 12%.3War was the second most cited source of anxiety in adolescents from Nottingham (133 (25%) of 538 aged 11-12; 127 (21%) of 626 1 Solantaus T, Rimpela M, Taipale V.The threat of war in the minds of 12-18 year olds in Finland.