Schwarz, S., M. Mustafić, and S. Junker. “Attachment to the Romantic Partner and Sibling: Attachment Hierarchies of Twins and Non-Twin Siblings”. Interpersona: An International Journal on Personal Relationships, Vol. 9, no. 2, Dec. 2015, pp. 169-83, doi:10.5964/ijpr.v9i2.195.