title: Qt creator Adding external library (still: Cannot open include file: 'GL/glew.h')
body: <p>I followed the instruction:</p>
  
  <ol>
  <li>In the Projects pane, open the project file (.pro).</li>
  <li>Right-click in the code editor to open the context menu and select Add Library....</li>
  </ol>
  
  <p><img src="https://i.stack.imgur.com/igNF6.jpg" alt="Add Library"></p>
  
  <p>Then the following lines were added into the pro file:</p>
  
  <pre><code>win32:CONFIG(release, debug|release): LIBS += -L$$PWD/D:/OpenGL/glew-1.5.4/lib/ -lglew32
  else:win32:CONFIG(debug, debug|release): LIBS += -L$$PWD/D:/OpenGL/glew-1.5.4/lib/ -lglew32d
  
  INCLUDEPATH += $$PWD/D:/OpenGL/glew-1.5.4/include
  DEPENDPATH += $$PWD/D:/OpenGL/glew-1.5.4/include
  </code></pre>
  
  <p>However, I click the green triangle icon on the bottom left the run the program, still get the errors:</p>
  
  <blockquote>
    <p>error: C1083: Cannot open include file: 'GL/glew.h': No such file or directory</p>
  </blockquote>