Research

Pulish Year

Type

Factors

Level

Wang Zhen [68]

2009

CR

② (−1) ⑥ (+1)

L

Duan Qingzhen [69]

2012

RCT

① (−2) ② (−1) ⑥ (+1)

L

Zeng Jibao [70]

2008

RCT

① (−2) ② (−1) ⑥ (+1)

L

Wu Xuehua [71]

2003

CR

① (−1) ② (−1) ⑥ (+1)

VL