As I am so bad at solving puzzles, including codes, ciphers and other cryptic and clandestine communication that I have to solve using various online toolboxes, I decided to take my revenge with this mystery. To decipher the code, you need to read either of the required books available from a local library. Books were published in 2005 by an American publisher. The code you will need was developed for radio communication at the end of the 20th century, and here we use the Vernam ciphered version of the code.
With the book, you'll easily find the cache at those coordinates:
C2:90:9B:36:74:44:24:70
37:F0:A7:64:74:44:24:70
Without the book... good luck!
You can verify your answer by reading the other book.