diff --git a/doc/supply_demand.rst b/doc/supply_demand.rst
index c3fe4cbf..c0cf2f4e 100644
--- a/doc/supply_demand.rst
+++ b/doc/supply_demand.rst
@@ -357,6 +357,10 @@ Inside each country the industrial demand is then distributed using the `Hotmaps
 
 
 *Iron and Steel*
+$$CO_2 + C→ 2 CO$$ 
+$$ 3 Fe_2O_3 + CO → 2 Fe_3O_4 + CO$$ 
+$$Fe_3O_4 + CO −−−→ 3 FeO + CO_2$$
+$$FeO + CO −−−→ Fe + CO_2$$
 
 *Chemicals Industry*