A comprehensive overview of white phosphorus, its use and recycling, by ESPP (European Sustainable Phosphorus Platform): https://www.phosphorusplatform.eu/images/scope/ScopeNewsletter136.pdf
Stowa feasibility report on Spodofos (in Dutch; English excerpt available on request): https://www.stowa.nl/sites/default/files/assets/PUBLICATIES/Publicaties%202021/STOWA%202021-57%20%20Spodofos.pdf
Stowa E-zine publication (in Dutch): https://www.stowa.nl/nieuws/spodofos-witte-fosfor-terugwinnen-uit-slibas