I dont know if there is any direct article on Subsidiary views. A Subsidiary view is created when a line item has different demensionality from the module defaults. You create two of these while working in the 102 Introduction to Modelbuilding class.
There are 3 ways to create a subsidiary view, you can have a line item that has different lists, time scale or versions from the module default. For example, lets say you have a module and you have added a Products list and Sales Rep list that had Time and Versions. If in one of the line items you did not need to have the Sales Rep list, you could use the Applies to column in blueprint to change the dimensionality to just include the Products. Once you did this, you would have created a subsidiary view because this line item would have Products, Versions and Time and that is different than the module defaults.
Here is the link to more information about blueprint. You can change a line items dimensionality by using the Time Scale, Versions or Applies to columns.