rtokens: The group demanded Wang 's release and said his detention was a dangerous signal China was returning to its Cultural Revolution days .
pos: NNP POS NN CC NNP NN MD RB VB VBN IN JJ NN .
tokens: Wang 's family and Hangzhou police could not be reached for immediate comment .
ltokens: Police also would not say why Wang was being sent to a study class -- a holdover from the chaotic 1966-76 Cultural Revolution -- or say when he would be released , the group said .