diff --git a/include/mbr.h b/include/mbr.h
index 86cbecb..b73923c 100644
--- a/include/mbr.h
+++ b/include/mbr.h
@@ -4,6 +4,9 @@
 #include <stdint.h>
 #include "chs.h"
 
+// https://wiki.osdev.org/MBR_(x86)
+// https://en.wikipedia.org/wiki/Master_boot_record
+
 typedef struct {
     uint8_t attributes;
     chs_encoded_t chs_first;
diff --git a/src/chs.c b/src/chs.c
index 02ecd88..96995e0 100644
--- a/src/chs.c
+++ b/src/chs.c
@@ -7,6 +7,8 @@ void chs_decode(const chs_encoded_t* enc, chs_t* chs)
     chs->cylinder = (((uint16_t)enc->b[1]) & 0xC0) << 2 | (uint16_t)enc->b[2];
 }
 
+// https://wiki.osdev.org/LBA
+
 uint32_t chs_to_lba(const chs_conf_t* conf, const chs_t* chs)
 {
     return (chs->cylinder * conf->num_heads + chs->head) * conf->num_sectors + (chs->sector - 1);