O. Buranruk, W. Eungpinichpong, T. Chunyachareun, N. Chompuyan, P. Kodwong, and P. Sawana, “Effect of Chi-Kung exercise on alteration of hip and trunk flexibility in adults aged 20-30 years”, Arch AHS, vol. 14, no. 3, pp. 230–237, Sep. 2002.