| title | ISBN-13 (ISBN-10) | year of publication |
|---|---|---|
| Educational research in five European socialist countries: a survey 1970-1972 øof Bulgaria Hungary Poland Romania Yugoslavia = Recherche pédagogique dans cinq pays socialistes européens | 978-92-82O-OOO1-4 (92-82O-OOO1-X) | 1973 |