Which calligrapher wrote the manuscript of offering sacrifices to nephews?

The Manuscript for Sacrificing a Nephew (full name: Ji Mingwen for Sacrificing a Nephew to Doctor Zanshan) is a running script paper calligraphy work created by Yan Zhenqing, a calligrapher of the Tang Dynasty, in the first year of Tang Ganyuan (758), and now it is collected in the National Palace Museum in Taipei.

The Manuscript of Sacrifice to My Nephew is a draft of memorial service for Yan Jiming, my nephew. * * * Twenty-three lines, with 234 words. This manuscript recounts how Yan Gaoqing and his son, the prefect of Changshan, stood up and loyal opposition when they rebelled in An Lushan, so that "the father was trapped in the child's death, and the nest fell over the egg" and took justice into the heart. Throughout the pen, the feeling is like a tide, the calligraphy is magnificent, and the vertical pen is bold and unconstrained, in one go.

The Manuscript for Sacrificing a Nephew, the Preface to Lanting by Wang Xizhi in the Eastern Jin Dynasty and Huangzhou Cold Food Post by Su Shi in the Northern Song Dynasty are both called "the three largest running scripts in the world" and also known as "the second running script in the world". Moreover, this manuscript is written in extreme grief and indignation, regardless of the clumsy work of pen and ink, so the words fluctuate with the calligrapher's mood, which is purely a natural expression of the spirit and peacetime work. This is rare in the whole history of calligraphy, so the Manuscript for Sacrificing a Nephew is one of the original ink works with great historical and artistic value.