Surely one README file is enough.

contrib/intarray/README

-This is an implementation of RD-tree data structure using GiST interface
-of PostgreSQL. It has built-in lossy compression - must be declared
-in index creation - with (islossy). Current implementation has index support 
-for one-dimensional array of int4's.
-All works was done by Teodor Sigaev (teodor@stack.net) and Oleg Bartunov
-(oleg@sai.msu.su).
-
-INSTALLATION:
-
-  gmake
-  gmake install
-  -- load functions
-  psql <database> < _int.sql 
-
-EXAMPLE USAGE:
-
-  create table message (mid int not null,sections int[]);
-  create table message_section_map (mid int not null,sid int not null);
-
-  -- create indices
-CREATE unique index message_key on message ( mid );
-CREATE unique index message_section_map_key2 on message_section_map (sid, mid );
-CREATE INDEX message_rdtree_idx on message using gist ( sections ) with ( islossy );
-
-  -- select some messages with section in 1 OR 2 - OVERLAP operator
-  select message.mid from message where message.sections && '{1,2}';  
-
-  -- select messages contains in sections 1 AND 2 - CONTAINS operator
-  select message.mid from message where message.sections @ '{1,2}';
-  -- the same, CONTAINED operator
-  select message.mid from message where '{1,2}' ~ message.sections;
-
-TEST:
-
-  subdirectory test contains test suite.
-  cd ./test
-  1. createdb TEST
-  2. psql TEST < ../_int.sql
-  3. ./create_test.pl | psql TEST
-  4. ./bench.pl - perl script to benchmark queries, supports OR, AND queries
-                  with/without RD-Tree. Run script without arguments to 
-                  see availbale options.
-
-     a)test without RD-Tree (OR)
-       ./bench.pl -d TEST -s 1,2 -v
-     b)test with RD-Tree 
-       ./bench.pl -d TEST -s 1,2 -v -r
-
-BENCHMARKS:
-
-Size of table <message>: 200000
-Size of table <message_section_map>: 268538 
-
-Distribution of messages by sections:
-
-section 0: 73899 messages
-section 1: 16298 messages
-section 50: 1241 messages
-section 99: 705 messages
-
-old - without RD-Tree support,
-new - with RD-Tree
-
-+----------+---------------+----------------+
-|Search set|OR, time in sec|AND, time in sec|
-|          +-------+-------+--------+-------+
-|          |  old  |  new  |   old  |  new  |
-+----------+-------+-------+--------+-------+
-|         1|  1.427|  0.215|       -|      -|
-+----------+-------+-------+--------+-------+
-|        99|  1.029|  0.018|       -|      -|
-+----------+-------+-------+--------+-------+
-|       1,2|  1.829|  0.334|   5.654|  0.042|
-+----------+-------+-------+--------+-------+
-| 1,2,50,60|  2.057|  0.359|   5.044|  0.007|
-+----------+-------+-------+--------+-------+