Media type: E-Article Title: Effectiveness of professional and paraprofessional helpers: A comment on Durlak Contributor: Nietzel, Michael T.; Fisher, Stuart G. Published: American Psychological Association (APA), 1981 Published in: Psychological Bulletin, 89 (1981) 3, Seite 555-565 Language: English DOI: 10.1037/0033-2909.89.3.555 ISSN: 1939-1455; 0033-2909 Keywords: History and Philosophy of Science ; General Psychology Origination: Footnote: