This App guide prepared for the game titled Call of Duty contains very precise description of going through all playable missions, which made up a campaign for a single player. In every description there are clues connecting to the ways of performing the given tasks and skillfully eliminating the enemies you meet on your way.
The additional advantage of this guidebook are clues, which help to find secret service data, here they are secrets. They are marked green in this description of completing the game. Moreover, at the end of the guide, there is a list of all secrets with bigger photos, which will help you to find them.