I defined the folowing function:
#####
def getOptions(label, table):
    return [(-1, 'Select %s' % (label))] +\
        sorted([(entry.id, str(entry)) for entry in table.select()],
               key = operator.itemgetter(1))
#####

I can be used with:
#####
    owner          = SingleSelectField(label     = ownerLabel,
                                       options   = getOptions(ownerLabel, Owner)
                                       default   = 1)
#####

In this way the select field starts with an entry that tells to select
a value. And after that it has on ordered list off all the values of
the foreign key.
I hope it is usefull for someone.

--
Cecil Westerhof