diff --git a/src/ELF/constants.jl b/src/ELF/constants.jl
index 09ecf98..8d8d582 100644
--- a/src/ELF/constants.jl
+++ b/src/ELF/constants.jl
@@ -1,3 +1,7 @@
+# These constants are in glibc and llvm:
+# * https://github.com/bminor/glibc/blob/969d7cf89966d55fbf0732ae7bc0949a970c837d/elf/elf.h
+# * https://github.com/llvm/llvm-project/blob/b2d7312d52f299a2f854c673796ad1a699e0d79f/llvm/include/llvm/BinaryFormat/ELF.h
+
 # e_ident[EIBCLASS]
 const ELFCLASSNONE = 0 #Invalid class
 const ELFCLASS32 = 1 #32-bit objects