TY  - JOUR
T1  - External Validity: A Forgotten Issue?
A1  - Palla,Sandro
A1  - Farella,Mauro
JO  - Journal of Oral & Facial Pain and Headache
VL  - 23
IS  - 4
SP  - 297
EP  - 298
SN  - 2333-0376
Y1  - 2009
ER  -