we compare the absolute and relative de rham–witt complexes considered by hesselholt and madsen (ann. sci. école norm. sup. 37 (2004), 1–43; ann. of math. (2) 158 (2003), 1–113) and by langer and zink (j. inst. math. jussieu 3 (2004), 231–314), which both generalize the classical de rham–witt complex of bloch, deligne, and illusie (ann. sci. école norm. sup. (4) 12 (1979), 501–661) from $\mathbb{f}_p$-schemes to $\mathbb{z}_{(p)}$-schemes. from this comparison, we derive a gauss–manin connection on the crystalline cohomology of x/wn(s) for a smooth family x/s.