Treble watch continues for Paris Saint-Germain and Barcelona, both of whom have already collected their first trophies of the season and are perhaps the most formidable candidates

The UEFA Champions League semifinals get underway on Tuesday, Apr. 29 with Arsenal taking on Paris Saint-Germain for the second time this European campaign.

How does it work?Thirty-six sides entered into the new "league phase" and now just four remain with a month-and-a-half to go in the UCL campaign.Barcelona, Paris Saint-Germain, Arsenal, and Inter Milan are through to the semifinals,