Glade Project Home Page: https://glade.pn.org/
PyGTK Wrapper Library Home Page: https://www.daa.com.au/~james/pygtk
Programmer Documentation for libglade: https://developer.gnome.org/doc/API/libglade/libglade.html
Gtk+ Project Home Page: https://www.gtk.org/
On-line Tutorial for Glade: https://linuxfocus.org/English/July2000/article160.shtml
Design Patterns: Elements of Reusable Object-Oriented Software by Gamma, Helm, Johnson and Vlissides (Addison-Wesley, 1994). Describes the Observer pattern, citing Smalltalk's Model-View-Controller framework as an early example of the pattern.