diff --git a/doc/about.rst b/doc/about.rst
index 62216161..41a75c71 100644
--- a/doc/about.rst
+++ b/doc/about.rst
@@ -49,7 +49,8 @@ Authors & Quotation
 
 **Developers**:
 
-- ver. 2.0
+
+- ver. 2.0-
 
   H. Shinaoka, J. Otsuki, K. Yoshimi, M. Kawamura, N. Takemori, Y. Motoyama
 
@@ -60,6 +61,7 @@ Authors & Quotation
   H. Shinaoka, J. Otsuki, K. Yoshimi, M. Kawamura, T. Kato
 
 **Related papers**:
+
 This package depends on TRIQS libraries and applications.
 Please cite relevant papers for these original libraries.
 
diff --git a/doc/support/faqs.rst b/doc/support/faqs.rst
index 178f1a92..337150a1 100644
--- a/doc/support/faqs.rst
+++ b/doc/support/faqs.rst
@@ -155,11 +155,25 @@ Can I use my impurity solver?
 Yes. Follow the instruction in :doc:`../impuritysolvers/how_to_integrate`
 
 
-
-
-
 ..
    ``dcore`` crashes abnormally when using cthyb
    ---------------------------------------------
 
    Please retry.
+
+
+Others
+-------
+
+DCore is slow even with MPI parallelization
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+One of the reasons is that the number of threads of each MPI process is not set properly.
+Unfortunately, the environment variable to set the number of threads is different among environments/libraries (OpenBLAS, Intel MKL, etc.).
+The followings are the environment variables to set the number of threads for some libraries.
+
+* OMP_NUM_THREADS
+* OPENBLAS_NUM_THREADS
+* MKL_NUM_THREADS
+* VECLIB_MAXIMUM_THREADS
+* NUMEXPR_NUM_THREADS