You tried going to https://politics.ubc.ca/fileadmin/user_upload/poli_sci/Faculty/warren/Separation_of_Powers_and_Westminster_Systems_Draft_1.pdf, and it doesn't exist. All is not lost! You can search for what you're looking for.
https://politics.ubc.ca/fileadmin/user_upload/poli_sci/Faculty/warren/Separation_of_Powers_and_Westminster_Systems_Draft_1.pdf