diff --git a/README.md b/README.md
index d717366..81ec6c5 100644
--- a/README.md
+++ b/README.md
@@ -30,6 +30,6 @@ JSchemeMin 是又一个JVM平台上的Scheme语言实现。
 
 目前，JSchemeMin 只提供解释器而非编译器。基本的性能监视机制已经存在。调试器和覆盖率工具也已经提供。
 
-性能并非JSchemeMin的主要设计目标，大部公情况下用明显的实现方式，不为性能牺牲实现的简单性，但相信足以满足预期的需要。
+性能并非JSchemeMin的主要设计目标，大部分情况下用明显的实现方式，不为性能牺牲实现的简单性，但相信足以满足预期的需要。
 
 本软件为自由软件: 你可以在自由软件基金会的GNU通用公共许可，版本3或按你的意愿更新的版本，的条款下再分发它和/或修改它。
diff --git a/doc/first.tex b/doc/first.tex
index 6b3812e..1590787 100644
--- a/doc/first.tex
+++ b/doc/first.tex
@@ -12,7 +12,8 @@
 \multicolumn{3}{c}{陈颂光 (\textit{Revisor})} \\
 \multicolumn{3}{c}{A\authorsc{LEX} S\authorsc{HINN},
 J\authorsc{OHN} C\authorsc{OWAN}, \authorsc{AND}
-A\authorsc{RTHUR} A. G\authorsc{LECKLER} (\textit{Editors})} \\
+A\authorsc{RTHUR} A. G\authorsc{LECKLER} } \\
+\multicolumn{3}{c}{\textit{(Editors, Revised$^{\mathit{7}}$ Report on the Algorithmic Language Scheme)}} \\
 \\
 S\authorsc{TEVEN} G\authorsc{ANZ} &
 A\authorsc{LEXEY} R\authorsc{ADUL} &
diff --git a/doc/r7rs.tex b/doc/r7rs.tex
index 627893e..b5b76e4 100644
--- a/doc/r7rs.tex
+++ b/doc/r7rs.tex
@@ -8,7 +8,7 @@
 \makeindex
 \input{commands}
 
-\def\headertitle{Revised$^{7}$ Scheme}
+\def\headertitle{JSchemeMin User Manual}
 \def\integerversion{7}
 
 % Sizes and dimensions
diff --git a/src/com/github/chungkwong/jschememin/Debugger.java b/src/com/github/chungkwong/jschememin/Debugger.java
index d2ef8f6..c836edd 100644
--- a/src/com/github/chungkwong/jschememin/Debugger.java
+++ b/src/com/github/chungkwong/jschememin/Debugger.java
@@ -85,9 +85,6 @@ private boolean isCaredPoint(){
 		return cont.hasNext()&&cont.getCurrentEvaluable()instanceof ExpressionEvaluator&&
 				caredExpressions.containsKey(cont.getCurrentValue());
 	}
-	private boolean isFinished(){
-		return cont.hasNext();
-	}
 	public ScmObject eval(ScmObject obj){
 		return new Evaluator(cont.getCurrentEnvironment()).eval(obj);
 	}
diff --git a/src/com/github/chungkwong/jschememin/lib/Java.java b/src/com/github/chungkwong/jschememin/lib/Java.java
index ed7cd69..ea78d5a 100644
--- a/src/com/github/chungkwong/jschememin/lib/Java.java
+++ b/src/com/github/chungkwong/jschememin/lib/Java.java
@@ -21,11 +21,9 @@
 import static com.github.chungkwong.jschememin.lib.Utility.car;
 import static com.github.chungkwong.jschememin.lib.Utility.cdr;
 import com.github.chungkwong.jschememin.type.*;
-import java.lang.invoke.*;
 import java.lang.reflect.*;
 import java.math.*;
 import java.util.*;
-import java.util.stream.*;
 /**
  *
  * @author Chan Chung Kwong <1m02math@126.com>
@@ -118,7 +116,6 @@ private static ScmObject invoke(ScmObject param)throws ClassNotFoundException
 		Object[] arguments=toArray(((ScmPair)param).getCddr());
 		Class[] paraType=toClassArray(arguments);
 		Method m=(Method)selectMethod(cls.getMethods(),method,paraType);
-		MethodHandle handle=MethodHandles.lookup().unreflect(m);
 		if(m!=null)
 			try{
 				return new ScmJavaObject(m.invoke(obj,adjustForVarargs(arguments,m)));
@@ -165,9 +162,6 @@ private static Object[] adjustForVarargs(Object[] args,Executable m){
 	private static ScmObject cast(ScmObject param) throws ClassNotFoundException{
 		return new ScmJavaObject(Class.forName(((ScmSymbol)cadr(param)).getValue()).cast(((ScmJavaObject)car(param)).getJavaObject()));
 	}
-	private static Set<Class> getPossibleReturnType(Class cls,String method){
-		return Arrays.stream(cls.getMethods()).filter((m)->m.getName().equals(method)).map((m)->m.getReturnType()).collect(Collectors.toSet());
-	}
 	private static Executable selectMethod(Executable[] choices,String name,Class[] argsType){
 		Executable best=null;
 		Class<?>[] bestParameterTypes=null;
diff --git a/src/com/github/chungkwong/jschememin/type/ScmSymbol.java b/src/com/github/chungkwong/jschememin/type/ScmSymbol.java
index d26d4f2..bed9792 100644
--- a/src/com/github/chungkwong/jschememin/type/ScmSymbol.java
+++ b/src/com/github/chungkwong/jschememin/type/ScmSymbol.java
@@ -25,7 +25,7 @@ public String getValue(){
 	}
 	@Override
 	public boolean equals(Object obj){
-		return getClass().equals(obj.getClass())&&((ScmSymbol)obj).id.equals(id);
+		return obj!=null&&getClass().equals(obj.getClass())&&((ScmSymbol)obj).id.equals(id);
 	}
 	@Override
 	public int hashCode(){
diff --git a/test/com/github/chungkwong/jschememin/LexTest.java b/test/com/github/chungkwong/jschememin/LexTest.java
index c1a8103..e64f22c 100644
--- a/test/com/github/chungkwong/jschememin/LexTest.java
+++ b/test/com/github/chungkwong/jschememin/LexTest.java
@@ -169,7 +169,7 @@ public void testRealNumber(){
 		check("1.e-10)",new ScmFloatingPointNumber(new BigDecimal("1e-10")),SimpleToken.getToken(")"));
 		Assert.assertSame(new Lex("+nan.0)").nextToken(),ScmSpecialReal.POSITIVE_NAN);
 		try{
-			Assert.assertSame(new Lex("+nan.0)").getRemainingTokens().size(),2);
+			Assert.assertEquals(new Lex("+nan.0)").getRemainingTokens().size(),2);
 			Assert.assertEquals(new Lex("+nan.0)").getRemainingTokens().get(1),SimpleToken.getToken(")"));
 		}catch(IOException ex){
 			Assert.assertTrue(false);