DOC: fix broken and redirected links

README.rst

@@ -52,7 +52,7 @@ If you use PyBLP in your research, we ask that you also cite `Conlon and Gortmak
 Installation
 ------------
 
-The PyBLP package has been tested on `Python <https://www.python.org/downloads/>`_ versions 3.6 through 3.9. The `SciPy instructions <https://scipy.org/install.html>`_ for installing related packages is a good guide for how to install a scientific Python environment. A good choice is the `Anaconda Distribution <https://www.anaconda.com/distribution/>`_, since it comes packaged with the following PyBLP dependencies: `NumPy <https://numpy.org/>`_, `SciPy <https://www.scipy.org/>`_, `SymPy <https://www.sympy.org/en/index.html>`_, and `Patsy <https://patsy.readthedocs.io/en/latest/>`_. For absorption of high dimension fixed effects, PyBLP also depends on its companion package `PyHDFE <https://github.com/jeffgortmaker/pyhdfe>`_, which will be installed when PyBLP is installed.
+The PyBLP package has been tested on `Python <https://www.python.org/downloads/>`_ versions 3.6 through 3.9. The `SciPy instructions <https://scipy.org/install/>`_ for installing related packages is a good guide for how to install a scientific Python environment. A good choice is the `Anaconda Distribution <https://www.anaconda.com/products/distribution>`_, since it comes packaged with the following PyBLP dependencies: `NumPy <https://numpy.org/>`_, `SciPy <https://scipy.org/>`_, `SymPy <https://www.sympy.org/en/index.html>`_, and `Patsy <https://patsy.readthedocs.io/en/latest/>`_. For absorption of high dimension fixed effects, PyBLP also depends on its companion package `PyHDFE <https://github.com/jeffgortmaker/pyhdfe>`_, which will be installed when PyBLP is installed.
 
 However, PyBLP may not work with old versions of its dependencies. You can update PyBLP's Anaconda dependencies with::
 

docs/references.rst

@@ -184,7 +184,7 @@ Newey, Whitney K., and Kenneth D. West (1987). `Hypothesis testing with efficien
 Owen (2013)
 ~~~~~~~~~~~
 
-Owen, Art B. (2013). `Monte Carlo theory, methods and examples <https://statweb.stanford.edu/~owen/mc/>`_.
+Owen, Art B. (2013). `Monte Carlo theory, methods and examples <https://artowen.su.domains/mc/>`_.
 
 
 Owen (2017)
@@ -211,12 +211,6 @@ Reynaerts, Varadhan, and Nash (2012)
 Reynaerts, Jo, Ravi Varadhan, and John C. Nash (2012). `Enhancing the convergence properties of the BLP (1995) contraction mapping <https://ideas.repec.org/p/ete/vivwps/35.html>`_. VIVES discussion paper 35.
 
 
-Skrainka (2012)
-~~~~~~~~~~~~~~~
-
-Skrainka, Benjamin S. (2012). `A large scale study of the small sample performance of random coefficient models of demand <https://papers.ssrn.com/sol3/papers.cfm?abstract_id=1942627>`_.
-
-
 Varadhan and Roland (2008)
 ~~~~~~~~~~~~~~~~~~~~~~~~~~
 

docs/testing.rst

@@ -1,7 +1,7 @@
 Testing
 =======
 
-Testing is done with the `tox <https://tox.readthedocs.io/en/latest/>`_ automation tool, which runs a `pytest <https://docs.pytest.org/en/latest/>`_-backed test suite in the ``tests/`` directory. This `FAQ <https://tox.readthedocs.io/en/latest/developers.html>`_ contains some useful information about how to use tox on Windows.
+Testing is done with the `tox <https://tox.wiki/en/latest/>`_ automation tool, which runs a `pytest <https://docs.pytest.org/en/latest/>`_-backed test suite in the ``tests/`` directory. This `FAQ <https://tox.wiki/en/latest/developers.html>`_ contains some useful information about how to use tox on Windows.
 
 
 Testing Requirements
@@ -20,7 +20,7 @@ If software is not installed, its associated tests will be skipped. Additionally
 Running Tests
 -------------
 
-Defined in ``tox.ini`` are environments that test the package under different python versions, check types, enforce style guidelines, verify the integrity of the documentation, and release the package. First, `tox <https://tox.readthedocs.io/en/latest/>`_ should be installed on top of an Anaconda installation. The following command can be run in the top-level ``pyblp`` directory to run all testing environments::
+Defined in ``tox.ini`` are environments that test the package under different python versions, check types, enforce style guidelines, verify the integrity of the documentation, and release the package. First, `tox <https://tox.wiki/en/latest/>`_ should be installed on top of an Anaconda installation. The following command can be run in the top-level ``pyblp`` directory to run all testing environments::
 
     tox
 

pyblp/options.py

@@ -32,8 +32,7 @@
 
     One instance in which extended precision can be helpful in the BLP problem is when there are a large number of near
     zero choice probabilities with small integration weights, which, under standard precision are called zeros when in
-    aggregate they are nonzero. For example, :ref:`references:Skrainka (2012)` finds that using long doubles is
-    sufficient to solve many utility floating point problems.
+    aggregate they are nonzero.
 
     The precision of ``numpy.longdouble`` depends on the platform on which NumPy is installed. If the platform in use
     does not support extended precision, using ``numpy.longdouble`` may lead to unreliable results. For example, on