diff --git a/.gitignore b/.gitignore
index be8bc34..12d3767 100644
--- a/.gitignore
+++ b/.gitignore
@@ -32,3 +32,6 @@ version.tex
 db/
 _minted-*/
 *.qgz
+
+.faux*
+*.pbf
diff --git a/IV/Makefile b/IV/Makefile
new file mode 100644
index 0000000..f9b22a8
--- /dev/null
+++ b/IV/Makefile
@@ -0,0 +1,23 @@
+# HACK HACK
+EMPTY :=
+SPACE := $(EMPTY) $(EMPTY)
+
+RIVERS ?= Visinčia Šalčia Žeimena Lakaja
+
+.faux_filter-rivers: .faux_import-osm
+	./filter-rivers-query.awk $(RIVERS) | ./db -f -
+	touch $@
+
+.faux_import-osm: lithuania-latest.osm.pbf .faux.db
+	PGPASSWORD=osm osm2pgsql \
+			   -c --multi-geometry \
+			   -H 127.0.0.1 -d osm -U osm \
+			   $<
+	touch $@
+
+.faux.db:
+	./db start
+	touch $@
+
+lithuania-latest.osm.pbf:
+	wget http://download.geofabrik.de/europe/lithuania-latest.osm.pbf
diff --git a/IV/db b/IV/db
index 238a0d5..8b76a19 100755
--- a/IV/db
+++ b/IV/db
@@ -28,6 +28,7 @@ _wait_for_postgres() {
 
 case ${1:-} in
     start)
+        _psql -qc '\q' 2>/dev/null && exit 0
         docker run -d --rm \
             -p 5432:5432 \
             -e POSTGRES_DBNAME=osm \
diff --git a/IV/filter-rivers-query.awk b/IV/filter-rivers-query.awk
new file mode 100755
index 0000000..f82101c
--- /dev/null
+++ b/IV/filter-rivers-query.awk
@@ -0,0 +1,12 @@
+#!/usr/bin/awk -f
+
+BEGIN {
+    print "DROP TABLE IF EXISTS rivers;";
+    printf "CREATE TABLE rivers AS SELECT name,way FROM planet_osm_line WHERE "
+    for (i = 1; i < ARGC; i++) {
+        printf "name='%s'", ARGV[i]
+        if (i != ARGC - 1)
+            printf " OR ";
+    }
+    print ";";
+}
diff --git a/IV/tests.sql b/IV/tests.sql
index 8560031..4c048b2 100644
--- a/IV/tests.sql
+++ b/IV/tests.sql
@@ -51,6 +51,9 @@ insert into selfcrossing select name, (self_crossing(ways)).* from inflections;
 create table demo_selfcrossing3 (name text, i bigint, way geometry);
 insert into demo_selfcrossing3 select name, generate_subscripts(ways, 1), unnest(ways) from selfcrossing;
 
+-- COMBINED
+drop table if exists demo_wm;
+create table demo_wm (name text, i bigint, way geometry);
 
 do $$
 declare
diff --git a/IV/wm.sql b/IV/wm.sql
index 93cd0c6..902f6b3 100644
--- a/IV/wm.sql
+++ b/IV/wm.sql
@@ -296,9 +296,9 @@ begin
   end loop;
 
   if l_type = 'ST_LineString' then
-    return geoms[1];
+    return bends[1];
   elseif l_type = 'ST_MultiLineString' then
-    return st_union(geoms);
+    return st_union(bends);
   end if;
 end
 $$ language plpgsql;