Create table error

Dear group,
Could you please suggest if my sql syntax is wrong for
creating the table:
my sql statements:
create table EXPERIMENT
(
exp_id serial,
exp_name varchar(32) not null,
con_id serial references
contacts(con_id),
exp_type varchar(32) not null,
exp_desc varchar(64),
exp_pmid integer(30) not null,
exp_rawdata_url varchar(32),
constraint experiment_pk primary
key(exp_id)
);

When I compile this I get the following error:
psql:/home/sk/temp/postgres/exp.sql:11: ERROR: syntax
error at or near "(" at character 200

What is wrong with my code.

Please help.

SK

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