Related Rule
Germany
Practice Relating to Rule 8. Definition of Military Objectives
Section G. Economic installations
Germany’s Military Manual (1992) provides that military objectives include, in particular, “economic objectives which make an effective contribution to military action (transport facilities, industrial plants, etc.)”. 
Germany, Humanitarian Law in Armed Conflicts – Manual, DSK VV207320067, edited by The Federal Ministry of Defence of the Federal Republic of Germany, VR II 3, August 1992, English translation of ZDv 15/2, Humanitäres Völkerrecht in bewaffneten KonfliktenHandbuch, August 1992, § 443.