Karl Dickson gets top billing

MATCH OFFICIAL APPOINTMENTS: Following a compelling start to the knock-out stages of the tournaments, EPCR announceD the referees for this weekend's quarterfinals of the Champions Cup and Challenge Cup.

England's Karl Dickson will take charge of the top billing clash of European heavyweights, Leinster and Stade Rochelais, at Dublin's Lansdowne Road on Saturday (April 13).

On the same day, the last-eight matches in the Champions Cup will kick off with the meeting of Union Bordeaux-Begles and Harlequins at Stade Chaban-Delmas which will be refereed by Andrea Piardi of Italy.

Also on Saturday, France's Mathieu Raynal has been appointed for what promises to be an intriguing confrontation between the in-form Northampton Saints and the Bulls at Franklin's Gardens.

The Champions Cup quarterfinals will conclude on Sunday (April 14) when Chris Busby of Ireland will be on the whistle for the tie which pits No.1-ranked Stade Toulousain against the Exeter Chiefs at Stade Ernest-Wallon.

The EPCR Challenge Cup quarterfinals get under way on Friday (April 12) when Pierre Brousset of France takes charge of the meeting of Gloucester and the Ospreys at Kingsholm, and then on Saturday, the Sharks versus Edinburgh and ASM Clermont Auvergne v Ulster fixtures will be refereed by England's Matthew Carley and Christophe Ridley respectively.

On Sunday, Mike Adamson of Scotland has been appointed for the clash of Benetton and Connacht at Stadio di Monigo.

Quarterfinals appointments

Champions Cup

Saturday, April 13

Union Bordeaux-Bègles v Harlequins

Referee: Andrea Piardi (Italy)

Assistant referees: Federico Vedovelli (Italy), Gianluca Gnecchi (Italy)

TMO: Stefano Penne (Italy)

Leinster v Stade Rochelais

Referee: Karl Dickson (England)

Assistant referees: Luke Pearce (England), Andrew Jackson (England)

TMO: Tom Foley (England)

Northampton Saints v Bulls

Referee: Mathieu Raynal (France)

Assistant referees: Ludovic Cayre (France), Luc Ramos (France)

TMO: Thomas Charabas (France)

Sunday, April 14

Stade Toulousain v Exeter Chiefs

Referee: Chris Busby (Ireland)

Assistant referees: Eoghan Cross (Ireland), Andy Brace (Ireland)

TMO: Mark Patton (Ireland)

Challenge Cup

Friday, April 12

Gloucester v Ospreys

Referee: Pierre Brousset (France)

Assistant referees: Tual Trainini (France), Jeremy Rozier (France)

TMO: Denis Grenouillet (France)

Saturday, April 13

Clermont Auvergne v Ulster

Referee: Christophe Ridley (England)

Assistant referees: Joe James (England), Hamish Smales (England)

TMO: Dean Richards (England)

Sharks v Edinburgh

Referee: Matthew Carley (England)

Assistant referees: Anthony Woodthorpe (England), Adam Leal (England)

TMO: Ian Tempest (England)

Sunday, April 14

Benetton v Connacht

Referee: Mike Adamson (Scotland)

Assistant referees: Ruairidh Campbell (Scotland), Sam Grove-White (Scotland)

TMO: Hollie Davidson (Scotland)