You may need a visum to enter Switzerland; please check the Swiss regulations. Note that Switzerland is not (yet) part of the Schengen area, that is, a Schengen visum does not necessarily extend to Switzerland.
On request, the organizers
send to you a letter of invitation for the Algo 2006 conference,
provided that at least one of the following two conditions hold.
Only
if at least one of these criteria apply to you, contact the
organizers, for example via algo06@inf.ethz.ch, and provide the
following information: