ERROR: relation "employees" does not exist

Hi,

I just installed Postgresql 9.2 on my Debian Wheezy system.

I want to study and learn about new data type, the range type.

I'm following the tutorial:
https://wiki.postgresql.org/images/7/73/Range-types-pgopen-2012.pdf

but when I run the command:
CREATE TABLE employee_schedule (
  id serial,
  employee_id integer REFERENCES employees(id),
  start_time timestamptz,
  end_time timestamptz
);

I get an error message:

NOTICE:  CREATE TABLE will create implicit sequence
"employee_schedule_id_seq" for serial column "employee_schedule.id"
ERROR:  relation "employees" does not exist

So how can I solve this problem?

--
Regards from Pal