Hi, you'll need to clarify which theorists you're expected to research with your tutor, they might include John Bowlby, Mary Ainsworth, Main and Solomon, Donald Winnicott
Theories look at the types of attachment, separation, anxiety, insecurity, the significant people in a child's life and objects that children can become emotionally attached to.
Foster Care unit 3 on OCR.org and on
minimumstandards.org positive behaviour and relationships
If you search for
'Mary' in the preview of this book on amazon there is a little reading on page 70
Best wishes xx