PPSR does not charge authors for any submission, article-processing or publication fee. We currently cover the cost of initial and ongoing publication activities from donations. Thus, the publication is absolutely free. However, we need donations to provide the infrastructure system for open access environment, develop and maintain electronic tools for peer review and publication, manuscript layout fees, and other expenses. If you wish to make a donation to PPSR, please write to the Editor-in-Chief at firstname.lastname@example.org.