Back to Yan 'an is a combination of folk songs in northern Shaanxi and modern poetry, so it can read the flavor of "believing in heaven" and is often used to repeat chapters and songs. Farewell to Cambridge is the representative work of Xu Zhimo and Crescent School, which stresses "three beauties" (beauty of rhythm, color and architecture). Bi Bingxin's four poems mainly express his love for his mother with concrete images; Ai Qing's My Missing is Round uses metaphor throughout, comparing invisible missing to tangible circle.