1. Contraction mappings in b-metric spaces;Czerwik;Acta Math. Inform. Univ. Ostravensis,1993
2. The contraction mapping principle in almost metric spaces;Bakhtin;Funkts. Anal. Gos. Ped. Inst. Ulyanovsk,1989
3. Lectures on Analysis on Metric Spaces;Heinonen,2001
4. KKM mappings in metric type spaces