“…Fourth order PDE filters (You et al, 2000), adaptive fourth order PDE filter (Samsonov et al, 2004), fourth order complex PDE filters (Rajan et al, 2009). Non local means filter (NLM) (Buades et al, 2005), fast NLM filter (Coupé et al, 2006), Block wise optimised NLM filter (Coupé et al, 2008), Unbiased NLM filter (Manjón et al, 2008), dynamic NLM filter (Gal et al, 2010), enhanced NLM filter (Liu et al, 2010), adaptive NLM filter (Manjón et al, 2010). Combination of domain and range filters (Tomasi et al, 1998), bilateral domain and range filters , trilateral domain and range filters .…”