Explain reformulation for SOS1ToMILP

Author: blegat

src/Bridges/Constraint/bridges/SOS1ToMILPBridge.jl

@@ -9,7 +9,14 @@
 
 `SOS1ToMILPBridge` implements the following reformulation:
 
-  * ``x \\in \\textsf{SOS1}(d)`` into a mixed-integer linear program.
+  * ``x \\in \\textsf{SOS1}(d)`` into the following mixed-integer linear program.
+
+Assuming ``l_i \\le x_i \\le u_i`` with finite bounds ``l_i, u_i``:
+```math
+z_i \\in \{0, 1\}
+\\sum z_i = 1
+l_i z_i \\le x_i \\le u_i z_i
+```
 
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