12 files changed, 187 insertions, 20 deletions
diff --git a/coq.html.markdown b/coq.html.markdown
index 4c1ad690..3a924a19 100644
--- a/coq.html.markdown
+++ b/coq.html.markdown
@@ -61,8 +61,8 @@ Locate "+".
 
 (* Calling a function with insufficient number of arguments does not cause
    an error, it produces a new function. *)
-Definition make_inc x y := x + y. (* make_inc is int -> int -> int *)
-Definition inc_2 := make_inc 2.   (* inc_2 is int -> int *)
+Definition make_inc x y := x + y. (* make_inc is nat -> nat -> nat *)
+Definition inc_2 := make_inc 2.   (* inc_2 is nat -> nat *)
 Compute inc_2 3. (* Evaluates to 5 *)
 
 
@@ -370,7 +370,7 @@ Close Scope string_scope.
           power series and results,...)
 • Relations : Relations (definitions and basic results)
 • Sorting : Sorted list (basic definitions and heapsort correctness)
-• Strings : 8-bits characters and strings
+• Strings : 8-bit characters and strings
 • Wellfounded : Well-founded relations (basic results)
  *)
 
@@ -472,7 +472,7 @@ Proof.
   intros A B ab.  destruct ab as [ a b ]. apply a.
 Qed.
 
-(* We can prove easily prove simple polynomial equalities using the
+(* We can easily prove simple polynomial equalities using the
    automated tactic ring. *)
 
 Require Import Ring.
diff --git a/de-de/nix-de.html.markdown b/de-de/nix-de.html.markdown
index ea02e81d..ffe8dffc 100644
--- a/de-de/nix-de.html.markdown
+++ b/de-de/nix-de.html.markdown
@@ -356,3 +356,6 @@ with builtins; [
 
 * [Susan Potter - Nix Cookbook - Nix By Example]
   (https://ops.functionalalgebra.com/nix-by-example/)
+  
+* [Rommel Martinez - A Gentle Introduction to the Nix Family]
+  (https://web.archive.org/web/20210121042658/https://ebzzry.io/en/nix/#nix)
diff --git a/docker.html.markdown b/docker.html.markdown
index 24f85247..1dad267a 100644
--- a/docker.html.markdown
+++ b/docker.html.markdown
@@ -3,9 +3,10 @@ language: docker
 filename: docker.bat
 contributors:
     - ["Ruslan López", "http://javapro.org/"]
+    - ["Michael Chen", "https://github.com/ML-Chen"]
 ---
 
-```
+```bat
 :: download, install and run hello-world image
 docker run hello-world
 
@@ -37,12 +38,12 @@ docker run hello-world
 :: For more examples and ideas, visit:
 :: https://docs.docker.com/get-started/
 
-:: now lets see currently running images
+:: now let's see currently running images
 docker ps
 :: CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS            
 ::   NAMES
 
-:: lets see the images we have ran previously
+:: let's see the images we have ran previously
 docker ps -a
 
 :: CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS                     PORTS     
@@ -54,7 +55,7 @@ docker ps -a
 :: let's remove our previously generated image
 docker rm happy_poincare
 
-:: lets test if it was really deleted
+:: let's test if it was really deleted
 docker ps -a
 :: CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS            
 ::   NAMES
@@ -89,7 +90,7 @@ docker ps -a
 ::                test_container
 :: as you can see the name is now what we have specified
 
-:: retireve logs from a named container
+:: retrieve logs from a named container
 docker logs test_container
 :: Hello from Docker!
 :: This message shows that your installation appears to be working correctly.
@@ -143,4 +144,4 @@ docker ps -a
 ::               nifty_goldwasser
 
 docker rm nifty_goldwasser
-```
-\ No newline at end of file
+```
diff --git a/es-es/typescript-es.html.markdown b/es-es/typescript-es.html.markdown
index c42da4a4..fbe1290b 100644
--- a/es-es/typescript-es.html.markdown
+++ b/es-es/typescript-es.html.markdown
@@ -12,7 +12,7 @@ TypeScript es un lenguaje cuyo objetivo es facilitar el desarrollo de aplicacion
 TypeScript añade conceptos comunes como clases, módulos, interfaces, genéricos y (opcionalmente) tipeo estático a JavaScript.
 Es un superset de JavaScript: todo el código JavaScript es código válido en TypeScript de manera que se puede integrar fácilmente a cualquier proyecto . El compilador TypeScript emite JavaScript.
 
-Este artículo se enfocará solo en la sintáxis extra de TypeScript, y no en [JavaScript] (../javascript/).
+Este artículo se enfocará solo en la sintáxis extra de TypeScript, y no en [JavaScript] (../javascript-es/).
 
 Para probar el compilador de TypeScript, diríjase al [Área de Pruebas] (http://www.typescriptlang.org/Playground) donde podrá tipear código, y ver como se auto-completa al tiempo que ve el código emitido JavaScript.
 
diff --git a/fr-fr/typescript-fr.html.markdown b/fr-fr/typescript-fr.html.markdown
index 52d34650..8a761f61 100644
--- a/fr-fr/typescript-fr.html.markdown
+++ b/fr-fr/typescript-fr.html.markdown
@@ -12,7 +12,7 @@ TypeScript est un langage visant à faciliter le développement d'applications l
 TypeScript ajoute des concepts classiques comme les classes, les modules, les interfaces, les génériques et le typage statique (optionnel) à JavaScript.
 C'est une surcouche de JavaScript : tout le code JavaScript est valide en TypeScript ce qui permet de l'ajouter de façon transparente à n'importe quel projet. Le code TypeScript est transcompilé en JavaScript par le compilateur.
 
-Cet article se concentrera seulement sur la syntaxe supplémentaire de TypeScript, plutôt que celle de [JavaScript] (../javascript/).
+Cet article se concentrera seulement sur la syntaxe supplémentaire de TypeScript, plutôt que celle de [JavaScript] (../javascript-fr/).
 
 Pour tester le compilateur de TypeScript, rendez-vous au [Playground] (http://www.typescriptlang.org/Playground) où vous pourrez coder, profiter d'une autocomplétion et accéder directement au rendu JavaScript.
 
diff --git a/pt-br/typescript-pt.html.markdown b/pt-br/typescript-pt.html.markdown
index ed76959c..7d28bf53 100644
--- a/pt-br/typescript-pt.html.markdown
+++ b/pt-br/typescript-pt.html.markdown
@@ -12,7 +12,7 @@ Typescript é uma linguagem que visa facilitar o desenvolvimento de aplicações
 Typescript acrescenta conceitos comuns como classes, módulos, interfaces, genéricos e (opcional) tipagem estática para JavaScript.
 É um super conjunto de JavaScript: todo o código JavaScript é TypeScript válido então ele pode ser adicionado diretamente a qualquer projeto. O compilador emite TypeScript JavaScript.
 
-Este artigo irá se concentrar apenas na sintaxe extra do TypeScript, ao contrário de [JavaScript](javascript-pt.html.markdown).
+Este artigo irá se concentrar apenas na sintaxe extra do TypeScript, ao contrário de [JavaScript](../javascript-pt/).
 
 Para testar o compilador TypeScript, vá para o [Playground](http://www.typescriptlang.org/Playground), onde você vai ser capaz de escrever código, ter auto conclusão e ver diretamente o JavaScript emitido.
 
diff --git a/python.html.markdown b/python.html.markdown
index e21d7dde..39e60455 100644
--- a/python.html.markdown
+++ b/python.html.markdown
@@ -482,7 +482,7 @@ except (TypeError, NameError):
     pass                 # Multiple exceptions can be handled together, if required.
 else:                    # Optional clause to the try/except block. Must follow all except blocks
     print("All good!")   # Runs only if the code in try raises no exceptions
-finally:                 #  Execute under all circumstances
+finally:                 # Execute under all circumstances
     print("We can clean up resources here")
 
 # Instead of try/finally to cleanup resources you can use a with statement
@@ -735,7 +735,7 @@ class Human:
         return "*grunt*"
 
     # A property is just like a getter.
-    # It turns the method age() into an read-only attribute of the same name.
+    # It turns the method age() into a read-only attribute of the same name.
     # There's no need to write trivial getters and setters in Python, though.
     @property
     def age(self):
diff --git a/set-theory.html.markdown b/set-theory.html.markdown
index 6be7aa00..ae8b5388 100644
--- a/set-theory.html.markdown
+++ b/set-theory.html.markdown
@@ -41,7 +41,7 @@ The cardinality, or size, of a set is determined by the number of items in the s
 For example, if `S = { 1, 2, 4 }`, then `|S| = 3`.
 
 ### The Empty Set
-* The empty set can be constructed in set builder notation using impossible conditions, e.g. `∅ = { x : x =/= x }`, or `∅ = { x : x ∈ N, x < 0 }`;
+* The empty set can be constructed in set builder notation using impossible conditions, e.g. `∅ = { x : x ≠ x }`, or `∅ = { x : x ∈ N, x < 0 }`;
 * the empty set is always unique (i.e. there is one and only one empty set);
 * the empty set is a subset of all sets;
 * the cardinality of the empty set is 0, i.e. `|∅| = 0`.
diff --git a/sv-se/nix-sv.html.markdown b/sv-se/nix-sv.html.markdown
index 15d9456b..647575fe 100644
--- a/sv-se/nix-sv.html.markdown
+++ b/sv-se/nix-sv.html.markdown
@@ -365,4 +365,7 @@ with builtins; [
   (https://medium.com/@MrJamesFisher/nix-by-example-a0063a1a4c55)
 
 * [Susan Potter - Nix Cookbook - Nix By Example]
-  (http://funops.co/nix-cookbook/nix-by-example/)
+  (https://ops.functionalalgebra.com/nix-by-example/)
+  
+* [Rommel Martinez - A Gentle Introduction to the Nix Family]
+  (https://web.archive.org/web/20210121042658/https://ebzzry.io/en/nix/#nix)
diff --git a/zh-cn/c-cn.html.markdown b/zh-cn/c-cn.html.markdown
index 7286fa9f..dbad5030 100644
--- a/zh-cn/c-cn.html.markdown
+++ b/zh-cn/c-cn.html.markdown
@@ -616,7 +616,7 @@ typedef void (*my_fnp_type)(char *);
 
 如果你有问题，请阅读[compl.lang.c Frequently Asked Questions](http://c-faq.com/)。
 
-使用合适的空格、缩进，保持一致的代码风格非常重要。可读性强的代码比聪明的代码、高速的代码更重要。可以参考下[Linux内核编码风格](https://www.kernel.org/doc/Documentation/CodingStyle)
+使用合适的空格、缩进，保持一致的代码风格非常重要。可读性强的代码比聪明的代码、高速的代码更重要。可以参考下[Linux内核编码风格](https://www.kernel.org/doc/Documentation/process/coding-style.rst)
 。
 除了这些，多多Google吧
 
diff --git a/zh-cn/java-cn.html.markdown b/zh-cn/java-cn.html.markdown
index 27003f3e..1de7f3e6 100644
--- a/zh-cn/java-cn.html.markdown
+++ b/zh-cn/java-cn.html.markdown
@@ -297,8 +297,8 @@ class Bicycle {
     // Bicycle 类的成员变量和方法
     public int cadence; // Public: 任意位置均可访问
     private int speed;  // Private: 只在同类中可以访问
-    protected int gear; // Protected: 可以在同类与子类中可以访问
-    String name; // default: 可以在包内中可以访问
+    protected int gear; // Protected: 可以在同类与子类中访问
+    String name; // default: 可以在包内访问
 
     // 构造函数是初始化一个对象的方式
     // 以下是一个默认构造函数
diff --git a/zh-cn/qt-cn.html.markdown b/zh-cn/qt-cn.html.markdown
new file mode 100644
index 00000000..8681c85b
--- /dev/null
+++ b/zh-cn/qt-cn.html.markdown
@@ -0,0 +1,160 @@
+---
+category: tool
+tool: Qt Framework
+language: c++
+filename: learnqt-cn.cpp
+contributors:
+    - ["Aleksey Kholovchuk", "https://github.com/vortexxx192"]
+translators:
+    - ["GengchenXU", "https://github.com/GengchenXU"]
+lang: zh-cn
+    
+---
+
+**Qt** Qt是一个广为人知的框架，用于开发跨平台软件，该软件可以在各种软件和硬件平台上运行，代码几乎没有变化，同时具有本机应用程序的能力和速度。虽然**Qt**最初是用*C*++，但也有其他语言的端口: *[PyQt](https://learnxinyminutes.com/docs/pyqt/)*, *QtRuby*, *PHP-Qt*, 等等.
+
+**Qt** 非常适合使用图形用户界面 （GUI） 创建应用程序。本教程是关于如何用*C++*去实现。
+
+```c++
+/*
+ * 让我们从最经典的开始
+ */
+
+// Qt框架的所有标头均以大写字母'Q'开头
+#include <QApplication>
+#include <QLineEdit>
+
+int main(int argc, char *argv[]) {
+	 // 创建一个对象来管理应用程序范围内的资源
+    QApplication app(argc, argv);
+
+    // 创建行编辑widgets并在屏幕上显示
+    QLineEdit lineEdit("Hello world!");
+    lineEdit.show();
+
+    // 启动应用程序的事件循环
+    return app.exec();
+}
+```
+
+**Qt**与 GUI 相关的部分与*widgets*及其之间的*connection*有关。
+
+[阅读更多有关widgets的信息](http://doc.qt.io/qt-5/qtwidgets-index.html)
+
+```c++
+/*
+ * 让我们创建一个标签和一个按钮。
+ * 按下按钮时应显示一个标签。
+ * Qt代码本身就可以说明问题。
+ */
+ 
+#include <QApplication>
+#include <QDialog>
+#include <QVBoxLayout>
+#include <QPushButton>
+#include <QLabel>
+
+int main(int argc, char *argv[]) {
+    QApplication app(argc, argv);
+
+    QDialog dialogWindow;
+    dialogWindow.show();
+    
+    // 添加垂直布局
+    QVBoxLayout layout;
+    dialogWindow.setLayout(&layout);  
+
+    QLabel textLabel("Thanks for pressing that button");
+    layout.addWidget(&textLabel);
+    textLabel.hide();
+
+    QPushButton button("Press me");
+    layout.addWidget(&button);
+    
+    // 按下按钮时显示隐藏标签
+    QObject::connect(&button, &QPushButton::pressed,
+                     &textLabel, &QLabel::show);
+
+    return app.exec();
+}
+```
+
+注意，*QObject :: connect*部分。 此方法用于将一个对象的*SIGNAL*连接到另一个对象的*SLOTS*。
+
+**Signals** 会被发出当对象发生某些事情时，例如当用户按下QPushButton对象时会发出*push*的信号。
+
+**Slots** 是可以响应于接收到的信号而执行的*action*。
+
+[阅读有关SLOTS和SIGNALS的更多信息](http://doc.qt.io/qt-5/signalsandslots.html)
+
+
+接下来，让我们了解到我们不仅可以使用标准的wigets，而且可以通过继承扩展其行为。 让我们创建一个按钮并计算其被按下的次数。 为此，我们定义了自己的类* CounterLabel *。 由于特定的Qt体系结构，必须在单独的文件中声明它。
+
+```c++
+// counterlabel.hpp
+
+#ifndef COUNTERLABEL
+#define COUNTERLABEL
+
+#include <QLabel>
+
+class CounterLabel : public QLabel {
+    Q_OBJECT  // 在每个自定义wiget中必须存在的Qt定义的宏
+
+public:
+    CounterLabel() : counter(0) {
+        setText("Counter has not been increased yet");  // QLabel方法
+    }
+
+public slots:
+    // 将响应按钮按下而调用的操作
+    void increaseCounter() {
+        setText(QString("Counter value: %1").arg(QString::number(++counter)));
+    }
+
+private:
+    int counter;
+};
+
+#endif // COUNTERLABEL
+```
+
+```c++
+// main.cpp
+// 与前面的示例几乎相同
+
+#include <QApplication>
+#include <QDialog>
+#include <QVBoxLayout>
+#include <QPushButton>
+#include <QString>
+#include "counterlabel.hpp"
+
+int main(int argc, char *argv[]) {
+    QApplication app(argc, argv);
+
+    QDialog dialogWindow;
+    dialogWindow.show();
+
+    QVBoxLayout layout;
+    dialogWindow.setLayout(&layout);
+
+    CounterLabel counterLabel;
+    layout.addWidget(&counterLabel);
+
+    QPushButton button("Push me once more");
+    layout.addWidget(&button);
+    QObject::connect(&button, &QPushButton::pressed,
+                     &counterLabel, &CounterLabel::increaseCounter);
+
+    return app.exec();
+}
+```
+
+当然，Qt框架比本教程介绍的部分要复杂得多，因此请仔细阅读和练习。
+
+## 进一步阅读
+- [Qt 4.8 tutorials](http://doc.qt.io/qt-4.8/tutorials.html)
+- [Qt 5 tutorials](http://doc.qt.io/qt-5/qtexamplesandtutorials.html)
+
+祝你好运，生活愉快!