RT Article T1 A mean squared error model for dual frame, mixed mode survey design JF Journal of the American Statistical Association VO 81 IS 396 SP 930 OP 937 A1 Lepkowski, James M. A2 Groves, Robert M. 1948- LA English YR 1986 UL https://krimdok.uni-tuebingen.de/Record/1912621398 DO 10.1080/01621459.1986.10478352