Sankey Diagrams in Google Charts

Notes on elements of advanced visualizations.  Sankey diagrams including multilevel forms, are available in Google Charts.   " ... A sankey diagram is a visualization used to depict a flow from one set of values to another. The things being connected are called nodes and the connections are called links. Sankeys are best used when you want to show a many-to-many mapping between two domains (e.g., universities and majors) or multiple paths through a set of stages (for instance, Google Analytics uses sankeys to show how traffic flows from pages to other pages on your web site). ...  "