sphinx>=4.3,<5
sphinx_book_theme>=0.2.0,<1

# higher versions requires sphinx 5
sphinxcontrib-applehelp<1.0.5
sphinxcontrib-devhelp<1.0.5
sphinxcontrib-htmlhelp<2.0.4
sphinxcontrib-serializinghtml<1.1.10
sphinxcontrib-qthelp<1.0.6
.
