Song Ke (1327-1387), Calligraphy in cursive script. Photo Sotheby's

signed Song Ke, with five collectors' seals, qian, pin yang li shi, wang yun lou cang, ceng wei zhi yu zhi shan zhai suo you, zi bo zhai zhu ren hu shi de yu jian cang: ink on paper, two album leaves: each 28.6 by 27.6 cm. 11 1/4  by 10 7/8  in. (2). Estimation 50,000 — 70,000 USD 

PROPERTY FROM A PRIVATE U.S. COLLECTION 

Litterature: Calligraphy of Ming and Qing Masters, Vol. 1, Jiang Zhaoshen, Tokyo: Nigensha, 1987, pp. 4, 5, 12-15 

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