040000 tree 5bff88722d855623614540223544823ee93122d9	impl
040000 tree edc379046735b2de8aaf926384b3b7c7fc1cacef	math
040000 tree 07c510d2c65e4918392e9ace05b41d2340f14a0e	text
040000 tree 48a97d3b2ca2c17f079141da08f68a3dd3c6417b	util