1. AENOR, 1999. Test for general properties of aggregates. Part 2: Methods for reducing laboratory samples. UNE-EN 932-2. Madrid.
2. AENOR, 1998. Test for geometrical properties of aggregates. Part 1: determination of particle size distribution. Sieving method. UNE-EN 933-1. Madrid.
3. AENOR, 1998. Test for chemical properties of aggregates. Part 1: Chemical analysis. UNE-EN 1744-1. Madrid.
4. APHA-AWWA-WPCF, 2001. Standard Methods For The Examination of Water and Wastewater (20th ed.). American Public Health Association, Washington DC.
5. Non-invasive methods for treating and removing sludge from subsurface flow constructed wetlands II;Behrends,2006