Section 5.10 "Quota Methods Variants" in Friedrich Pukelsheim: Proportional Representation, Apportionment Methods and Their Applications, With a Foreword by Andrew Duff MEP, Second Edition. Springer International Publishing AG, Cham (CH) 2017. doi:10.1007/978-3-319-64707-4, E-Book ISBN 978-3-319-64707-4, Softcover ISBN 978-3-319-64706-7
