fixed copy paste errors and used erf and ExpModNormal and SkewNormal pdfs
fixed copy paste errors and used erf and ExpModNormal and SkewNormal pdfs

stan-dev/math,stan-dev/math,stan-dev/math,stan-dev/stan,stan-dev/math,stan-dev/stan,stan-dev/math,stan-dev/stan,stan-dev/stan,stan-dev/stan,stan-dev/math,stan-dev/math,stan-dev/math,stan-dev/math