M	Number of zones (circular bands) covering the entire territorial area concerned by vaccination.
n	number of vaccination centres belonging to the same zone.
d	Quantity of vaccines demanded by vaccination centre.
C	Load capacity of the drone
N	optimum number of drones used for the logistic distribution.
(k1, k2, …, kN)/k1 $\ge$ k2 $\ge$, …, $\ge$ kN, with ${\displaystyle \sum }_{i=1}^N{k}_i=n$, where ki is the number of vaccinations centres visited by the ith drone.
k1(d)	denotes the maximum number of vaccination centres that one drone can serve, according to the domain D of d.
G = {n, N, (k1, k2, …, kN)}	Graph defining the set of paths followed by the N drones in order to deliver vaccines to the n vaccinations centres belonging the same zone. For instance, the path described by the ith drone is formed by the set of locations or vertices to be visited and the set of directed links connecting them.
2 r	The radius of the first zone. It represents also the width of circular bands.