TY  - JOUR
A1  - Ellgring, Johann Heinrich
T1  - Comment to J. Rojahn: "Validity and reliability of data from naturalistic observational studies - problems and alternatives"
N2  - No abstract available
Y1  - 1978
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-42520
ER  -