The student is quoting from a blog by pediatrician Nadine Burke Harris. The blog entry is undated.

Pediatrician Nadine Burke Harris stated that her clinical experience shows that child-parent psychotherapy “is best practice doing healing work with children experiencing toxic stress.”

Pediatrician Nadine Burke Harris (n.d.) stated that her clinical experience shows that child-parent psychotherapy “is best practice doing healing work with children experiencing toxic stress.”

For a work with no date, the abbreviation “n.d.” is used in parentheses following the author’s name.