Zhu Yunming (1460-1526), Letters. Photo: Sotheby's.

signed Yunming, Yunming, with five collectors' seals, zi bo zhai zhu ren hu shi de yu jian cang, song ling jing zhao tu shu, li da, wang yun lou, qian (2); ink on paper, album leaves; 22.2 by 9.5 cm. 8 3/4  by 3 3/4  in. (and various sizes). Estimation 20,000 — 30,000 USD 

Litterature: Calligraphy of Ming and Qing Masters, Vol. 1, Jiang Zhaoshen, Tokyo: Nigensha, 1987, pp. 10, 11, 40-45 

Sotheby's. Fine Classical Chinese Paintings & Calligraphy. New York | 19 sept. 2013 - http://www.sothebys.com