Here is a list of all files with brief descriptions:

doc
include
band_pass
band_pass.h
bpf_2.h	Second-order band-pass filter
band_stop
band_stop.h	Band-stop filter module
bsf_2.h	Second-order band-stop filter
high_pass
high_pass.h	High-pass filter module
hpf_1.h	First-order high-pass filter
hpf_2.h	Second-order high-pass filter
limiter
limiter.h	Signal limiter module
srl.h	Slew-rate limiter
low_pass
low_pass.h	Low-pass filter module
lpf_1.h	First-order low-pass filter
lpf_2.h	Second-order low-pass filter
ma.h	Moving-average low-pass filter
filters.h	Main header for the Filters library
src
band_pass
bpf_2.tpp
band_stop
bsf_2.tpp
high_pass
hpf_1.tpp
hpf_2.tpp
limiter
srl.tpp
low_pass
lpf_1.tpp
lpf_2.tpp
ma.tpp