1. Ölhydraulik: Grundlagen, Bauelemente, Anwendungen;Bauer,2009
2. Directional spool valves, pilot-operated, with hydraulic or electro-hydraulic actuation: Type WEH and WHhttps://www.boschrexroth.com/en/xc/myrexroth/mediadirectory?language=de-DE&publication=NET&filterMediatype=1584&search_query=24751&search_action=submit&edition_enum=rd24751
3. Directly operated and pilot operated directional control valves: Series D1VW/D1DW/D3W/D3DW/D31DW/D41VW/D81VW/D91VWhttps://www.parker.com/Literature/Hydraulic%20Controls%20Europe/Manuals%20UK/DCV1-662%20UK.pdf