diff --git a/docs/demo_notebooks/modeltools/four-bar_linkage_model_and_simulation.ipynb b/docs/demo_notebooks/modeltools/four-bar_linkage_model_and_simulation.ipynb
index b7e9f68..1c2585c 100644
--- a/docs/demo_notebooks/modeltools/four-bar_linkage_model_and_simulation.ipynb
+++ b/docs/demo_notebooks/modeltools/four-bar_linkage_model_and_simulation.ipynb
@@ -37,8 +37,8 @@
     "from symbtools.modeltools import Rz # Rotationsmatrix in the xy plane (c, -s; s, c)\n",
     "import scipy.integrate as sc_integrate\n",
     "import matplotlib.pyplot as pl\n",
-    "from assimulo.solvers import IDA # Imports the solver IDA from Assimulo\n",
-    "from assimulo.problem import Implicit_Problem # Imports the problem formulation from Assimulo\n",
+    "from assimulo.solvers import ODASSL # Imports the solver ODASSL from Assimulo\n",
+    "from assimulo.problem import Overdetermined_Problem # Imports the problem formulation from Assimulo\n",
     "import ipydex\n",
     "plt = pl\n",
     "\n",
@@ -867,13 +867,13 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "model = Implicit_Problem(dae.model_func, yy0, yyd0, t0)\n",
+    "model = Overdetermined_Problem(dae.model_func, yy0, yyd0, t0)\n",
     "model.name = 'fourbar linkage'\n",
     "\n",
     "# indicate which components of y are differential (1) and which are purely algebraic (0)\n",
     "# model.algvar = dae.diff_alg_vars ##:\n",
     "\n",
-    "sim = IDA(model)\n",
+    "sim = ODASSL(model)\n",
     "# sim.suppress_alg = True #Necessary to set to True for >1 index problem\n",
     "\n",
     "# values <= 30 produce lots of output\n",