https://books.google.bg/books?id=b3Ydd6ocC88C&pg=PA159&lpg=PA159&dq=overhauser+splines&source=bl&ots=foSyK4itmh&sig=j8MzTJvk9VZhhXrxTqeNZaMF7JE&hl=bg&sa=X&ved=0ahUKEwj096emw8rJAhUFIA8KHTT3B9g4FBDoAQgnMAI#v=onepage&q=overhauser%20splines&f=false