Quote from the bottom of the paper: "This is a U.S. government work and its text is not subject to copyright protection in the United States; however, its text

Quote from the bottom of the paper: "This is a U.S. government work and its text is not subject to copyright protection in the United States; however, its text may be subject to foreign copyright protection 2018" However, Springer is still saying that you have to pay them $39.95 in order to get a pdf of the paper that probably costs them a few cents to deliver.