It's a poem written by Li Yining on the eve of graduation of Economics Department of Peking University. 1985, on the occasion of the 30th anniversary of graduation, according to his own experience in Peking University, Li Yining expanded this seven-line poem into "Partridge Sky": "The brook under the stone ditch is clear, never looking back, inclusive and extremely broad. If the valley is empty, it will swim by itself. My heart is silent, I miss my rest, but I have no intention of sinking sand, but I have become a continent. I should be like this all my life. I only intend to cultivate Mo Wen. "