Ystrom, E., Reichborn-Kjennerud, T., Tambs, K., Magnus, P., Torgersen, A. M. and Gustavson, K. (2014) “Multiple births and maternal mental health from pregnancy to 5 years after birth: A longitudinal population-based cohort study”, Norsk Epidemiologi, 24(1-2). doi: 10.5324/nje.v24i1-2.1823.