Plastics piping systems for non-pressure underground drainage and sewerage – Structured-wall piping systems of unplasticized poly(vinyl chloride) (PVC-U), polypropylene (PP) and polyethylene (PE) – Part 4: Guidance for the assessment of conformity; German version CEN/TS 13476-4:2008
standard by Deutsches Institut Fur Normung E.V. (German National Standard), 10/01/2008

Plastics piping systems for non-pressure underground drainage and sewerage – Structured-wall piping systems of unplasticized poly(vinyl chloride) (PVC-U), polypropylene (PP) and polyethylene (PE) – Part 4: Guidance for the assessment of conformity; German version CEN/TS 13476-4:2013
standard by Deutsches Institut Fur Normung E.V. (German National Standard), 07/01/2013