Study selection:
All papers identified through the database search and through manual
search of reference lists were checked to remove any duplicates.
Following this, study selection was carried out through three phases.
First, all titles were screened against the inclusion and exclusion
criteria. Second, abstracts from articles selected in the first phase
were screened against the same criteria. Third, full texts of articles
retrieved from the second phase were reviewed to check for eligibility
for inclusion in the review.