Reasons in favor of a Hubble-Lemaitre-Slipher's (HLS) law

Abstract: Based on historical facts, revisited from a present-day perspective, and on the documented opinions of the scientists involved in the discovery themselves, strong arguments are given in favor of a proposal to include prominent astronomer Vesto Slipher to the suggested addition of Georges Lema^itre's name to Hubble's law on the expansion of the Universe, and thus eventually call it Hubble-Lema^itre-Slipher's (HLS) law.