Weak $(1,1)$ estimate for maximal truncated rough singular integral operator

In their seminal work (Amer. J. Math. 78: 289-309, 1956), Calderón and Zygmund introduced the maximal truncated rough singular integral operator and established its $L^p$-boundedness for $1<p<\mathrm{\infty }$. However, the endpoint case $p=1$ remained an open problem. This paper resolves this problem. More precisely, we prove that the maximal truncated rough singular integral operator is of weak type $(1,1)$.