diff --git a/README.md b/README.md
index 2f51ef5..977cc70 100644
--- a/README.md
+++ b/README.md
@@ -38,3 +38,19 @@ sage: GC.cohomology_basis(4,6)
 ```
 
 Extensive examples of the use of this software are contained in the author's PhD dissertation: [*The action of Kontsevich's graph complex on Poisson structures and star products: an implementation*](https://doi.org/10.25358/openscience-9274).
+
+## Installation in a virtual Python environment (no SageMath installation required)
+
+Create and activate a virtual environment:
+
+    cd /path/to/gcaops-master/
+    python3 -m venv venv_gcaops
+    . venv_gcaops/bin/activate
+
+Install the package in the virtual environment:
+
+    pip install ".[passagemath]"
+
+This automatically installs the modularized parts of the Sage library that are
+needed by the package. (These modularized distributions are provided by
+https://github.com/passagemath.)
diff --git a/gcaops/util/directed_graph_sage.py b/gcaops/util/directed_graph_sage.py
index cd99eed..b8bc826 100644
--- a/gcaops/util/directed_graph_sage.py
+++ b/gcaops/util/directed_graph_sage.py
@@ -1,6 +1,9 @@
 import subprocess
 import os
-import sage.all # make SageMath work when called from Python
+try:
+    import sage.all # make SageMath work when called from Python
+except ImportError:
+    import sage.all__sagemath_graphs
 from sage.env import SAGE_NAUTY_BINS_PREFIX
 from sage.graphs.digraph import DiGraph
 from sage.graphs.graph import Graph
diff --git a/gcaops/util/formality_graph_sage.py b/gcaops/util/formality_graph_sage.py
index 5d49d0b..f48833d 100644
--- a/gcaops/util/formality_graph_sage.py
+++ b/gcaops/util/formality_graph_sage.py
@@ -1,7 +1,10 @@
 import itertools
 import subprocess
 import os
-import sage.all # make SageMath work when called from Python
+try:
+    import sage.all # make SageMath work when called from Python
+except ImportError:
+    import sage.all__sagemath_graphs
 from sage.env import SAGE_NAUTY_BINS_PREFIX
 from sage.graphs.digraph import DiGraph
 from gcaops.graph.formality_graph import FormalityGraph
diff --git a/gcaops/util/undirected_graph_sage.py b/gcaops/util/undirected_graph_sage.py
index e1bca8f..436af65 100644
--- a/gcaops/util/undirected_graph_sage.py
+++ b/gcaops/util/undirected_graph_sage.py
@@ -1,6 +1,9 @@
 import subprocess
 import os
-import sage.all # make SageMath work when called from Python
+try:
+    import sage.all # make SageMath work when called from Python
+except ImportError:
+    import sage.all__sagemath_graphs
 from sage.env import SAGE_NAUTY_BINS_PREFIX
 from sage.graphs.graph import Graph
 from gcaops.graph.undirected_graph import UndirectedGraph
diff --git a/setup.cfg b/setup.cfg
index 285de5b..0bf40ac 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -20,3 +20,12 @@ classifiers =
 packages = find:
 python_requires = >= 3
 install_requires =
+
+[options.extras_require]
+passagemath =
+    passagemath-graphs
+    passagemath-groups
+    passagemath-modules
+    passagemath-nauty
+    passagemath-plot
+    passagemath-repl
diff --git a/tox.ini b/tox.ini
new file mode 100644
index 0000000..1c19a15
--- /dev/null
+++ b/tox.ini
@@ -0,0 +1,9 @@
+[tox]
+envlist = passagemath
+
+[testenv:passagemath]
+extras =
+     passagemath
+
+commands =
+     python3 -c "from sage.all__sagemath_categories import QQ; from gcaops.all import *; GC = UndirectedGraphComplex(QQ, implementation='vector', sparse=True); GC.cohomology_basis(4,6)"