diff --git a/DESCRIPTION b/DESCRIPTION
index b037311..cb2413e 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -13,7 +13,8 @@ Suggests:
     knitr,
     rmarkdown,
     sybil,
-    sybilSBML
+    sybilSBML,
+    glpkAPI
 Description: For a given set of stoichiometric reactions, this package
     evaluates the mass and charge balance, extracts all reactants, products, orphan
     metabolites, metabolite names and compartments. Also are included some options
diff --git a/vignettes/MINVALintroduction.Rmd b/vignettes/MINVALintroduction.Rmd
index 7262052..487241e 100644
--- a/vignettes/MINVALintroduction.Rmd
+++ b/vignettes/MINVALintroduction.Rmd
@@ -20,6 +20,8 @@ install.packages("minval")
 ```{r, message=FALSE}
 library("minval")
 library("sybilSBML")
+library("sybil")
+library("glpkAPI")
 ```
 ### Metabolic Models
 Metabolic models are sets of stoichiometric reactions that represents a process where a set of chemical compounds called reactants are converted into others called products. In a stoichiometric reaction, all the reactants are placed on the left and the products on the right separated by an arrow symbol which indicates the direction of the reaction. Some examples of valid stoichiometric reactions are: