  We report a closed-form formula for the Zhang-Zhang polynomial (aka ZZ
polynomial or Clar covering polynomial) of an important class of elementary
pericondensed benzenoids $Rb\left(n_{1},n_{2},m_{1},m_{2}\right)$ usually
referred to as ribbons. A straightforward derivation is based on the recently
developed interface theory of benzenoids [Langner and Witek, MATCH Commun.
Math. Comput. Chem. 84, 143--176 (2020)]. The discovered formula provides
compact expressions for various topological invariants of
$Rb\left(n_{1},n_{2},m_{1},m_{2}\right)$: the number of Kekul\'e structures,
the number of Clar covers, its Clar number, and the number of Clar structures.
The last two classes of elementary benzenoids, for which closed-form ZZ
polynomial formulas remain to be found, are hexagonal flakes
$O\left(k,m,n\right)$ and oblate rectangles $Or\left(m,n\right)$.
