try to fix docs

Maximilian-Stefan-Ernst · Maximilian-Stefan-Ernst · commit 9ecc9c5b64bd · 2026-01-31T13:18:27.000+01:00
diff --git a/docs/src/tutorials/concept.md b/docs/src/tutorials/concept.md
@@ -104,6 +104,8 @@ SemConstant
 SemOptimizer
 ```
 
+A reference: [NLopt engine](@ref Base.get_extension(StructuralEquationModels, :SEMNLOptExt).SemOptimizerNLopt)
+
 ```@autodocs
 Modules = [
     Base.get_extension(StructuralEquationModels, :SEMNLOptExt),
