 Therefore, the concept of " tree-based " phylogenetic networks, which was introduced by Francis and Steel, has attracted much attention of theoretical biologists in the last few years.
<coherence>  Therefore, the concept of " tree-based " phylogenetic networks, which was introduced by Francis and Steel, has attracted much attention of theoretical biologists in the last few years.
 In the last few years, therefore, tree-based " phylogenetic networks, which was introduced by Francis and Steel, has attracted much attention of theoretical biologists in the last few years.