diff --git a/1_introduction.tex b/1_introduction.tex
index 5c2d1a1..82b947a 100644
--- a/1_introduction.tex
+++ b/1_introduction.tex
@@ -70,6 +70,8 @@ The main contributions of the paper are as follows:
 	when seeking a project with adequate profile documentation to participate in.
 	\item Describing the maintenance practice of community profile documentation from different aspects, 
 	which can act as a  reference for OSS maintainers in managing and ** the profile documentation in their repositories.
+	% 根据大环境，评价自身的维护情况的好坏
+	
 \end{itemize}
 
 
diff --git a/2_background.tex b/2_background.tex
index fcdf439..df6fc22 100644
--- a/2_background.tex
+++ b/2_background.tex
@@ -23,7 +23,7 @@ established a scheme of meaningful categories, and explored the frequency of dif
 They found that 
 the most common categories are relating to how to use the project and what the project is about.
 Additionally,
-they ****
+they proposed a classifier to automatically annotate the sections of \RDM files.
 
 
 Vendome \etal~\cite{Vendome2017License} studied the usage and change of OSS licenses in 16,221 Java projects.
@@ -39,6 +39,17 @@ They conducted queries on both GitHub and Google and presented 11 \COD  that wer
 The content of \COD was summarized as specifying the expectations against community participants' behaviour 
 in order to creating a friendly and inclusive community.
 
+
+Elazhary \etal~\cite{elazhary2019not} studied on 72 GitHub projects using CI tools~\cite{Yu:2015b}, 
+and examined the content of their \CON files.
+They found five main themes around contribution guidelines,
+including 
+project Orientation, contribution workflow, and pull request acceptance criteria.
+Also, 
+their examination of the actual activity trace data uncovered  
+contribution practices that were not introduced in the \CON files.
+
+
 % readme
 % license
 % code of conduct
diff --git a/4_4.tex b/4_4.tex
index 4aa7bac..4e957d7 100644
--- a/4_4.tex
+++ b/4_4.tex
@@ -155,7 +155,7 @@ For example,
 ``link'' occurs frequently in the update events of \RDM, \CON, and \TMP files,
 which means that the links contained in the  three kinds of documents needs to be often changed (added, modified or deleted).
 Additionally,
-\LIC files are changed more frequently to update the copyright ``year'', 
+\LIC files are changed more frequently to update the copyright ``year'' and ``version'', 
 and \RDM files often set the ``badg[e]''~\cite{2018Adding}.
 
 
diff --git a/9_ref.bib b/9_ref.bib
index 9019f5a..508b0d2 100644
--- a/9_ref.bib
+++ b/9_ref.bib
@@ -1,3 +1,21 @@
+@inproceedings{Yu:2015b,
+  title={Quality and productivity outcomes relating to continuous integration in GitHub},
+  author={Vasilescu, Bogdan and Yu, Yue and Wang, Huaimin and Devanbu, Premkumar and Filkov, Vladimir},
+  booktitle={Proceedings of the 10th Joint Meeting on Foundations of Software Engineering},
+  pages={805-816},
+  year={2015},
+}
+
+@inproceedings{elazhary2019not,
+  title={Do as I Do, Not as I Say: Do Contribution Guidelines Match the GitHub Contribution Process?},
+  author={Elazhary, Omar and Storey, Margaret-Anne and Ernst, Neil and Zaidman, Andy},
+  booktitle={2019 IEEE International Conference on Software Maintenance and Evolution (ICSME)},
+  pages={286--290},
+  year={2019},
+  organization={IEEE}
+}
+
+
 @Misc{github,
 howpublished = {\url{http://github.com}},
 note = {Accessed: 2020-08-14},