The phrase "Ti na zemlji a na nebu Bog" is not a formal book or guide, but rather a common expression in Balkan folk culture, music, and religious tradition. It frequently appears in songs, such as those by Posavski Odjeci or Milica Pavlović, and relates to the phrase "Bog na nebu, a na zemlji kum" or to the "Our Father" prayer. Ti na zemlji a na nebu Bog - Spotify