Update paper.md

Co-Authored-By: Claudio Moroni <43729990+ClaudMor@users.noreply.github.com>
Co-Authored-By: Pietro Monticone <38562595+pitmonticone@users.noreply.github.com>

Author: 3 people

paper/paper.md

@@ -63,7 +63,7 @@ The two main data structures are `MultilayerGraph` and `MultilayerDiGraph`: coll
 
 The **vertices** of a multilayer graph are representations of one set of distinct objects called `Node`s. Each layer may represent all the node set or just a subset of it. The vertices of `Multilayer(Di)Graph` are implemented via the `MultilayerVertex` custom type. Each `MultilayerVertex` encodes information about the node it represents, the layer it belongs to and its metadata. 
 
-Both the **intra-layer** and **inter-layer* *edges** are embedded in the `MultilayerEdge` struct, whose arguments are the two connected multilayer vertices, the edge weight and its metadata. It's important to highlight that `Multilayer(Di)Graph`s are weighted and able to store metadata by default (i.e. they have been assigned the `IsWeighted` and `IsMeta` traits from [SimpleTraits.jl](https://github.com/mauro3/SimpleTraits.jl)). 
+Both the **intra-layer** and **inter-layer edges** are embedded in the `MultilayerEdge` struct, whose arguments are the two connected multilayer vertices, the edge weight and its metadata. It's important to highlight that `Multilayer(Di)Graph`s are weighted and able to store metadata by default (i.e. they have been assigned the `IsWeighted` and `IsMeta` traits from [SimpleTraits.jl](https://github.com/mauro3/SimpleTraits.jl)). 
 
 The **layers** are implemented via the `Layer` struct composed of an underlying graph and a mapping from its integer-labelled vertices to the collection of `MultilayerVertex`s the layer represents. **Interlayers** are similarly implemented via the `Interlayer` mutable struct, and they are generally constructed by providing the two connected layers, the (multilayer) edge list between them and a graph. This usage of underlying graphs allows for an easier debugging procedure during construction and a more intuitive analysis afterwards allowing the package to leverage all the features of the JuliaGraphs ecosystem so that it can be effectively considered as a real proving ground of its internal consistency.