Δ Modals of speculation: explanation (pdf)
Δ Useful links from BBC Learning English, with a grammar reference section and exercices – including audio activities:
BBC Learning English – Course: intermediate / Unit 6 / Grammar Reference
http://www.bbc.co.uk/learningenglish/course/intermediate/unit-6/session-2/activity-1
http://www.bbc.co.uk/learningenglish/english/course/intermediate/unit-6/session-2/activity-2
http://www.bbc.co.uk/learningenglish/course/intermediate/unit-6/session-2/activity-3
http://www.bbc.co.uk/learningenglish/course/upper-intermediate/unit-25/session-1
