The notation cl co (A) I stumbled upon this notation, (cl co(A+C), while reading "Set Optimization—A Rather Short Introduction" by Andreas H. Hamel, Frank Heyde, Andreas Löhne, Birgit Rudloff and Carola Schrage.

Is it right for me to assume that cl co(A) means the convex closure of the set A?
I'm pretty sure that $\mathrm{cl}$ is the set closure operation. I'm less sure about $\mathrm{co}$, but I've seen it being used for the convex hull operation in other contexts.

As a reference, in Fundamentals of Convex Analysis, the same notations are used to refer to the closed convex hull of a set: