Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Flowchart diagram of the research: the starting subset has been obtained from Scopus database after the application of the inclusion criteria; tag 2 identifies very relevant documents; tag 1 labels documents with some relevant information; tag 0 collects not pertinent documents.
