A recent study found no evidence of seasonal affective disorder in Iceland where the sun does not appear for a long time in the winter.
The study was done by a group of scientists from california
It does not really say who did the study, so it is neither incorrect or correct.
( z1 study :ARG0 ( z2 group :cxnsistof ( z3 scientist :source ( z4 state :name ( z5 name :op "California" ) ) ) ) )