Why query takes soo much time

Dear all,
I have a query on 3 tables in a database as :-

_*Explain Analyze Output :-*_

explain anayze select c.clause, s.subject ,s.object , s.verb,
s.subject_type , s.object_type ,s.doc_id ,s.svo_id from clause2 c, svo2
s ,page_content p where c.clause_id=s.clause_id and s.doc_id=c.source_id
and c.sentence_id=s.sentence_id and s.doc_id=p.crawled_page_id order by
s.svo_id limit 1000 offset 17929000

"Limit (cost=21685592.91..21686802.44 rows=1000 width=2624) (actual
time=414601.802..414622.920 rows=1000 loops=1)"
" -> Nested Loop (cost=59.77..320659013645.28 rows=265112018116
width=2624) (actual time=0.422..404902.314 rows=17930000 loops=1)"
" -> Nested Loop (cost=0.00..313889654.42 rows=109882338
width=2628) (actual time=0.242..174223.789 rows=17736897 loops=1)"
" -> Index Scan using pk_svo_id on svo2 s
(cost=0.00..33914955.13 rows=26840752 width=2600) (actual
time=0.157..14691.039 rows=14238271 loops=1)"
" -> Index Scan using idx_clause2_id on clause2 c
(cost=0.00..10.36 rows=4 width=44) (actual time=0.007..0.008 rows=1
loops=14238271)"
" Index Cond: ((c.source_id = s.doc_id) AND
(c.clause_id = s.clause_id) AND (c.sentence_id = s.sentence_id))"
" -> Bitmap Heap Scan on page_content p (cost=59.77..2885.18
rows=2413 width=8) (actual time=0.007..0.008 rows=1 loops=17736897)"
" Recheck Cond: (p.crawled_page_id = s.doc_id)"
" -> Bitmap Index Scan on idx_crawled_id
(cost=0.00..59.17 rows=2413 width=0) (actual time=0.005..0.005 rows=1
loops=17736897)"
" Index Cond: (p.crawled_page_id = s.doc_id)"
"Total runtime: 414623.634 ms"

_*My Table & index definitions are as under :-

*_Estimated rows in 3 tables are :-

clause2 10341700
svo2 26008000
page_content 479785

CREATE TABLE clause2
(
id bigint NOT NULL DEFAULT nextval('clause_id_seq'::regclass),
source_id integer,
sentence_id integer,
clause_id integer,
tense character varying(30),
clause text,
CONSTRAINT pk_clause_id PRIMARY KEY (id)
)WITH ( OIDS=FALSE);
CREATE INDEX idx_clause2_id ON clause2 USING btree (source_id,
clause_id, sentence_id);

CREATE TABLE svo2
(
svo_id bigint NOT NULL DEFAULT nextval('svo_svo_id_seq'::regclass),
doc_id integer,
sentence_id integer,
clause_id integer,
negation integer,
subject character varying(3000),
verb character varying(3000),
"object" character varying(3000),
preposition character varying(3000),
subject_type character varying(3000),
object_type character varying(3000),
subject_attribute character varying(3000),
object_attribute character varying(3000),
verb_attribute character varying(3000),
subject_concept character varying(100),
object_concept character varying(100),
subject_sense character varying(100),
object_sense character varying(100),
subject_chain character varying(5000),
object_chain character varying(5000),
sub_type_id integer,
obj_type_id integer,
CONSTRAINT pk_svo_id PRIMARY KEY (svo_id)
)WITH ( OIDS=FALSE);
CREATE INDEX idx_svo2_id_dummy ON svo2 USING btree (doc_id,
clause_id, sentence_id);

CREATE TABLE page_content
(
content_id integer NOT NULL DEFAULT
nextval('page_content_ogc_fid_seq'::regclass),
wkb_geometry geometry,
link_level integer,
isprocessable integer,
isvalid integer,
isanalyzed integer,
islocked integer,
content_language character(10),
url_id integer,
publishing_date character(40),
heading character(150),
category character(150),
crawled_page_url character(500),
keywords character(500),
dt_stamp timestamp with time zone,
"content" character varying,
crawled_page_id bigint,
CONSTRAINT page_content_pk PRIMARY KEY (content_id),
CONSTRAINT enforce_dims_wkb_geometry CHECK (st_ndims(wkb_geometry) = 2),
CONSTRAINT enforce_srid_wkb_geometry CHECK (st_srid(wkb_geometry) = (-1))
)WITH ( OIDS=FALSE);
CREATE INDEX idx_crawled_id ON page_content USING btree
(crawled_page_id);
CREATE INDEX pgweb_idx ON page_content USING gin
(to_tsvector('english'::regconfig, content::text));

If possible, Please let me know if I am something wrong or any alternate
query to run it faster.

Thanks