Test Mermaid diagram

Author: ivan-pi

README.md

@@ -22,6 +22,27 @@ This version is a modernization of the original Fortran 77 code. This is a work
 
 Further updates are planned...
 
+### Decision tree
+
+Decision tree for systems of nonlinear equations
+
+```mermaid
+flowchart TB
+	start(Is the Jacobian matrix available?)
+	middle1(Is flexibility required?)
+	middle2(Is flexibility required?)
+	start --- Yes ---> middle1
+	start --- No ---> middle2
+	b1(HYBRJ)
+	b2(HYBRJ1)
+	b3(HYBRD)
+	b4(HYBRD1)
+	middle1 --- Yes ---> b1
+	middle1 --- No ---> b2
+	middle2 --- Yes ---> b3
+	middle2 --- No ---> b3
+```
+
 ### Documentation
 
  * The API documentation for the latest default branch can be found [here](https://fortran-lang.github.io/minpack/).  This is generated by processing the source files with [FORD](https://github.com/Fortran-FOSS-Programmers/ford).