fixing typo #2

Author: behrisch

docs/JOSS/paper.md

@@ -69,7 +69,7 @@ Simulating a transportation system microscopically requires a solid framework th
 
 # Statement of need
 
-Microscopic simulations of multi-modal transportation networks require a description of the network, and a detailed plan how objects (motorized and non-motorized vehicles, persons, goods) move through such a network. In the case of SUMO, this is achieved by assigning a route to each object in the simulation network that it has to follow from origin to destination, starting at a particular moment in time. The sum of all these trips is the so called origin-destination matrix, which is generally time-dependent. SUMO excels especially at the detailed modelling of how individual objects move in transportation networks. It is weaker, however, when it comes to the computation of the demand itself, which can be achieved by other, more dedicated tools like [TAPAS](https://github.com/DLR-VF/TAPAS/) [@Heinrichs.2017] or MATSim [@MATSim:2016].
+Microscopic simulations of multi-modal transportation networks require a description of the network, and a detailed plan how objects (motorized and non-motorized vehicles, persons, goods) move through such a network. In the case of SUMO, this is achieved by assigning a route to each object in the simulation network that it has to follow from origin to destination, starting at a particular moment in time. The sum of all these trips is the so called origin-destination matrix, which is generally time-dependent. SUMO excels especially at the detailed modelling of how individual objects move in transportation networks. It is weaker, however, when it comes to the computation of the demand itself, which can be achieved by other, more dedicated tools like [TAPAS](https://github.com/DLR-VF/TAPAS/) [@Heinrichs:2017] or MATSim [@MATSim:2016].
 
 For larger networks, an additional step is needed to transfer the demand (the time-dependent OD-matrix) into real routes that the various objects follow through the network. This is called the dynamic traffic assignment, which assumes that there is a kind of equilibrium between the demand and the supply given by the network. This fairly old (first ideas are from 1924), but still prevailing concept was formalized by @Wardrop:1952 and @BeckmannEtAl:1955, and comes in several flavours such as user equilibrium (UE), stochastic user equilibrium (SUE) etc. SUMO contains several tools to compute these equilibria, again in the form of python scripts that repeatedly start the simulation with changing routes, until such an equilibrium is achieved.