Table 1.

Summary of modeling variables.

Parameters
$c_{0i}^p$	Unit delivery cost from government to distribution center $i$ for PPE $p$
$c_{ij}^p$	Unit delivery cost from distribution center $i$ to local store $j$ for PPE $p$
$c_{jk}^p$	Unit delivery cost from local store $j$ to demand source $k$
$r_m^{p,{(t-s)}^{+}}$	Revenue earned per unit delivery of PPE $p$ to demand source type $m$ for demand period $s$ in period $t$
$L$	Local store certification cost
$A_{pt}$	Stock available to government for PPE $p$ in time period $t$
$C_j$	Inventory holding capacity at local store $j$
$d_{km}^{ps}$	Demand for PPE $p$ in period $s\in T$ originating from demand source $k$ and of type $m$
$l_{0i}$	Delivery (or lead) time from government to distribution center $i$
$l_{ij}$	Delivery (or lead) time from distribution center $i$ to local store $j$
$l_{jk}$	Delivery (or lead) time from local store $j$ to demand source $k$
Decision variables
$x_{0i}^{pt}$	#. units of PPE $p$ delivered from node 0 to distribution center $i$ during time period $t$
$y_{ij}^{pt}$	#. units of PPE $p$ delivered from distribution center $i$ to local store $j$ during time period $t$
$z_{jkm}^{pts}$	#. units of PPE $p$ delivered from local store $j$ to demand source $k$ of type $m$ for demand period $s$ in period $t$
${\omega }_j$	Equals 1 if local store $j\in J$ is used
$I_i^{pt}$	Stock level for PPE $p$ in period $t$ at distribution center $i$
$I_j^{pt}$	Stock level for PPE $p$ in period $t$ at local store $j$