RT Article T1 The effects of closely spaced and widely spaced sibship size on intellectual development JF American sociological review VO 64 IS 2 SP 199 OP 206 A1 Guo, Guang A2 VanWey, Leah K. LA English YR 1999 UL https://krimdok.uni-tuebingen.de/Record/1639755187 K1 Intelligenzentwicklung K1 Geschwisteranzahl