diff --git a/blog-langref.tex b/blog-langref.tex
index c12bee6..de5c789 100644
--- a/blog-langref.tex
+++ b/blog-langref.tex
@@ -47,7 +47,7 @@
 \renewcommand{\optional}[1]{} %uncomment for published version
 \mkclean
 
-\newcommand{\blogversion}{0.9\xspace}
+\newcommand{\blogversion}{0.10\xspace}
 
 \title{The \bl Language Reference  \\
 {\large (\bl version \blogversion)}
@@ -957,6 +957,20 @@ \section{Issuing queries}\label{query-section}
 \end{blogcode}
 
 
+\section{Input/Output}
+BLOG provides an utility function to load data from a file. 
+\blog|loadRealMatrix(filename)|
+\blog|loadRealMatrix(filename, row-num)|
+
+The data must contain same number of columns in each row, and separated by commas or spaces. 
+
+For example, to load feature matrix from the file "feature.txt".
+\begin{blogcode}
+fixed RealMatrix feature = loadRealMatrix("feature.txt");
+\end{blogcode}
+
+To output the results to a file, one can issue the command with the option \verb|-o [filename]| and \verb|--writer [writer-class-name]|. The latter is used to specify the output format. Valid options are \verb|blog.io.TableWriter| (default), \verb|blog.io.JsonWriter|, and \verb|blog.io.DummyWriter| (for omitting output).
+
 
 \section{Extending \bl}\label{extending-section}
 \input{extending.tex}
@@ -1109,11 +1123,6 @@ \section{Built-in distributions}\label{builtin-distribution-appendix}
 %% import urn-ball;
 %% \end{blogcode}
 %% 
-%% \subsection{Referring to external library}\label{-section}
-%% \begin{blogcode}
-%% extern blog.distribution.*;
-%% \end{blogcode}
-%% It will make all implementation of Distribution visible to blog inference engine.
 %% 
 %% 
 %% \section{Variable size array}\label{-section}
diff --git a/built-in-funcs.tex b/built-in-funcs.tex
index 7239dba..a864e9a 100644
--- a/built-in-funcs.tex
+++ b/built-in-funcs.tex
@@ -14,7 +14,7 @@ \subsection{Unary operators}
 \midrule
 \verb|-| & Integer & Integer & minus \\
 \verb|-| & Real & Real & minus \\
-\verb|-| & RealMatrix & RealMatrix & minus \\
+%\verb|-| & RealMatrix & RealMatrix & minus \\ % not supported yet
 \verb|!| & Boolean & Boolean & negation \\
 \bottomrule
 \end{tabular}
@@ -106,38 +106,72 @@ \subsection{Matrix operations}
 that the function \verb|eye| takes a single \verb|Integer| and produces a
 \verb|RealMatrix|.
 
-\blog|RealMatrix inv(RealMatrix x)|
-\myindent Inverse of the matrix \verb|x|.
+\blog|RealMatrix abs(RealMatrix m)|
+\myindent Element-wise absolute value.
 
-\blog|RealMatrix transpose(RealMatrix x)|
-\myindent Transpose of the matrix \verb|x|.
+\blog|RealMatrix colsum(RealMatrix m)|
+\myindent Column-wise sum of a matrix.
+For example, \verb|colsum([1, 2; 3, 4])| returns \verb|[4, 6]|.
 
 \blog|Real det(RealMatrix x)|
 \myindent Determinant of the matrix \verb|x|.
 
-\blog|Real trace(RealMatrix x)|
-\myindent Trace of the matrix \verb|x|, i.e. the sum of the elements on the diagonal.
-
 \blog|RealMatrix diag(RealMatrix vals)|
 \myindent Diagonal matrix with the given values on the diagonal. \verb|vals|
 must be a column vector.
 
-\blog|RealMatrix repmat(RealMatrix m, Integer rows, Integer cols)|
-\myindent Return the matrix \verb|m| tiled \verb|rows| times vertically and
-\verb|cols|
-times horizontally.
+\blog|RealMatrix exp(RealMatrix m)|
+\myindent Element-wise exponential of a matrix.
 
-\blog|RealMatrix sum(RealMatrix m)|
-\myindent Column-wise sum of a matrix.
-For example, \verb|sum([1, 2; 3, 4])| returns \verb|[4, 6]|.
+\blog|RealMatrix getcol(RealMatrix m, Integer i)|
+\myindent get i-th column of a matrix.
+
+\blog|RealMatrix getcols(RealMatrix m, Integer i, Integer j)|
+\myindent return a sub-matrix from i-th (inclusive) to j-th (inclusive) column of a matrix.
+
+\blog|RealMatrix getrow(RealMatrix m, Integer i)|
+\myindent get i-th row of a matrix.
+
+\blog|RealMatrix getrows(RealMatrix m, Integer i, Integer j)|
+\myindent return a sub-matrix from i-th (inclusive) to j-th (inclusive) row of a matrix.
 
 \blog|RealMatrix hstack(RealMatrix arg1, ...)|
 \blog|RealMatrix hstack(Real arg1, ...)|
 \myindent Stack scalars or matrices horizontally. Accepts an arbitrary number
-of
-arguments.
+of arguments.
 For example, \verb|hstack(1, 2, 3)| returns the row vector {\tt [1, 2, 3]}.
 
+\blog|RealMatrix inv(RealMatrix x)|
+\myindent Inverse of the matrix \verb|x|.
+
+\blog|RealMatrix log(RealMatrix m)|
+\myindent Element-wise logarithm of a matrix.
+
+\blog|Real matsum(RealMatrix m)|
+\myindent Total sum of a matrix.
+For example, \verb|matsum([1, 2; 3, 4])| returns \verb|10|.
+
+\blog|Integer numrows(RealMatrix m)|
+\myindent Number of rows of a matrix.
+
+\blog|Integer numcols(RealMatrix m)|
+\myindent Number of columns of a matrix.
+
+\blog|RealMatrix rowsum(RealMatrix m)|
+\myindent Row-wise sum of a matrix.
+For example, \verb|rowsum([1, 2; 3, 4])| returns \verb|[[3, 7]]|.
+
+\blog|RealMatrix transpose(RealMatrix x)|
+\myindent Transpose of the matrix \verb|x|.
+
+\blog|Real trace(RealMatrix x)|
+\myindent Trace of the matrix \verb|x|, i.e. the sum of the elements on the diagonal.
+
+\blog|RealMatrix repmat(RealMatrix m, Integer rows, Integer cols)|
+\myindent Return the matrix \verb|m| tiled \verb|rows| times vertically and
+\verb|cols|
+times horizontally.
+
 \blog|RealMatrix vstack(RealMatrix arg1, ...)|
 \blog|RealMatrix vstack(Real arg1, ...)|
 \myindent Stack scalars or matrices vertically. Accepts an arbitrary number of
@@ -156,11 +190,7 @@ \subsection{Matrix operations}
 \myindent Matrix of the given size, filled with ones.
 For example, \verb|ones(3, 4)| returns a 3x4 matrix of ones.
 
-\blog|RealMatrix abs(RealMatrix m)|
-\myindent Element-wise absolute value.
 
-\blog|RealMatrix exp(RealMatrix m)|
-\myindent Element-wise exponential of a matrix.
 
 Use square brackets to index into a matrix. If \verb|m| is a two-dimensional
 matrix, \verb|m[i]| returns the \verb|i|-th row of \verb|m|. If \verb|m| is a
@@ -268,3 +298,7 @@ \subsection{Miscellaneous functions}
 \blog|RealMatrix loadRealMatrix(String s)|
 \myindent Load a \verb|RealMatrix| from a text file. The space-separated
 formats produced by numpy and Matlab are supported.
+
+\blog|RealMatrix loadRealMatrix(String s, Integer i)|
+\myindent Load i-th line as a \verb|RealMatrix| from a text file. 
+The space-separated formats produced by numpy and Matlab are supported.
\ No newline at end of file
diff --git a/extending.tex b/extending.tex
index 3d17faf..b875493 100644
--- a/extending.tex
+++ b/extending.tex
@@ -15,8 +15,8 @@ \subsection{User-defined functions}\label{user-defined-function-section}
 
 import blog.model.AbstractFunctionInterp;
 
-public class Log10Interp extends AbstractFunctionInterp {
-  public Log10Interp(List args) {
+public class Log10 extends AbstractFunctionInterp {
+  public Log10(List args) {
   }
 
   public Object getValue(List args) {
@@ -26,17 +26,18 @@ \subsection{User-defined functions}\label{user-defined-function-section}
 }
 \end{minted}
 
-To use this function from a model, declare it like this:
+To use an externally defined function, a proper declaration should be added in the blog file using \verb|extern| keyword. 
 
+For example, to declare an externally defined 10-based logarithm. 
 \begin{blogcode}
-fixed Real log10(Real val) = my_package.Log10Interp();
+extern Real Log10(Real x);
 \end{blogcode}
 
-Then \verb|log10| can be used just like any other fixed function, e.g.
-\verb|query log10(100.0)|.
+Then \verb|Log10| can be used just like any other fixed function, e.g.
+\verb|query Log10(100.0)|.
 
-Make sure \verb|my_package| is on the class path. If you get an error like "No
-definition found for non-random function log10", you most likely have a
+Make sure \verb|Log10|  the same as the defined Class name in Java.If you get an error like "No
+definition found for non-random function Log10", you most likely have a
 class-path problem. If \verb|my_package| is in the current working directory,
 you need not do anything. Otherwise, if \verb|my_package| lives at
 \verb|/some/absolute/path/my_package|, launch \bl with an environment variable:
@@ -50,6 +51,13 @@ \subsection{User-defined functions}\label{user-defined-function-section}
 
 \subsection{User-defined distributions}\label{user-defined-distribution-section}
 
+For externally defined distribution, we need to add declaration of its signature in blog using \verb|distribution|.
+
+For example, to declare a \verb|UniformReal| distribution. 
+\begin{blogcode}
+distribution Real UniformReal(Real a, Real b);
+\end{blogcode}
+
 Probability distributions are implemented in Java.  Distribution classes should implement the interface \verb|blog.distrib.CondProbDistrib|. 
 By default, the \bl engine will look up distribution classes in the package \verb|blog.distrib|. In addition, it will look up distribution classes under the default empty package. 
 
diff --git a/readme.md b/readme.md
index 00e08e9..87d9180 100644
--- a/readme.md
+++ b/readme.md
@@ -7,7 +7,7 @@
 
 2. install Pygments 
   This package requires pygments package. You may install by 
-  easy_install Pygments
+  sudo easy_install Pygments
 
 3. install blog_py_lexer
   Latex highlighting needs the blog_py_lexer.