The term "nèijiā" usually refers to Wudangquan or the internal styles of Chinese martial arts, which Sun Lutang identified in the 1920s as T'ai Chi Ch'uan, Xíngyìquán and Bāguàzhǎng. This classifies most other martial arts as "wàijiā" (lit. "external/outside sect"). Some other Chinese arts, such as Liuhebafa, Bak Mei Pai, Bok Foo Pai and Yiquan are frequently classified (or classify themselves) as internal or having internal qualities (aka External/Internal styles). These secondary neijia may be related to, or derived from, the primary arts