In order to include them in the information extraction stage (Stage 3), the 4,342 literature items screened at Stage 2 had to meet the following criteria:
Er mwyn eu cynnwys yn y cam echdynnu gwybodaeth (Cam 3), roedd rhaid i’r 4,342 o eitemau llenyddiaeth a sgriniwyd yng Ngham 2 gwrdd â’r meini prawf canlynol: