What is the correct crew procedure for an unreliable airspeed alert?
As you probably know this is the situation that occurred for AF-447 (Rio-Paris) on June 2009. From the BEA report:

The accident resulted from the following succession of events:

Temporary inconsistency between the measured airspeeds, likely following the obstruction of the Pitot probes by ice crystals that led
in particular to autopilot disconnection and a reconfiguration to
alternate law, [...]
The crew not making the connection between the loss of indicated airspeeds and the appropriate procedure,


This mistake happened previously. From the same report:

Four crews did not identify the unreliable airspeed  situation: in two
cases, the crews concluded that there was an inconsistency between the
angles of attack; in the two other cases, the crew considered that the
speeds were erroneous rather than unreliable.

Then the procedure that should be used in case of unreliable airspeed:

The philosophy for processing the anomaly is described in the
“UNRELIABLE AIRSPEED INDICATION / ADR CHECK PROCEDURE” that is in
Flight Manual (AFM) and transcribed in the Airbus FCOM and the Air
France Operations Manual.


This procedure which is to be known without the support of the documentation gives time to retrieve data from the documentation (this is what you wanted to know):

See also:

Unreliable Airspeed Indications on SKYbrary.