In this paper we present a new characterization and perspective on a neutral to the right prior. This characterization is based on a sequence of predictive laws which provides explicitly the posterior parameters and Bayes estimators for such a prior.
"A characterization of a neutral to the right prior via an extension of Johnson’s sufficientness postulate." Ann. Statist. 27 (2) 589 - 599, April 1999. https://doi.org/10.1214/aos/1018031208