function goBack(e) {
        e.preventDefault();

        if(currentSection === globalSection)
            return;

        currentSection = currentSection.parentSection;

        // Since users click directly on sub-chapters of the main chapters, don't go back to main
        // chapters.
        if(currentSection.parentSection === globalSection)
            currentSection = globalSection;

        renderCurrentSection();
    }
**********************************************************************
    /* Go back to the previous section