Čudo dvadesetog vijeka: Marijina poruka iz Fatime

This is the first systematic book in the Croatian language dedicated to the Fatima apparitions (1917). Petrov wrote the work in the midst of World War II, on the occasion of the 25th anniversary of the apparition of Our Lady of Fatima to the three shepherds (Lucia, Franjo and Jacinta). He signed the book as "brother Stanko" and dedicated it to "his Croatian people".

The work provides a popular-spiritual account of the Fatima events: a description of the apparition, the secrets of Our Lady of Fatima, the miracle of the sun on October 13, 1917, a message of penance, the prayer of the rosary and the consecration of Russia to the Heart of Mary. The author interprets Fatima as a great miracle of the 20th century and a warning to humanity against the horrors of war, communism and the moral crisis.

The style is pious, accessible and appealing, typical of Catholic popular literature of that time. The book has a strong patriotic and spiritual tone, calling the Croatian people to conversion and prayer in difficult times of war.

Today, this is a rare antiquarian book. It has significant cultural and historical value as the first Croatian record of Fatima and a testimony to the faith of the Croatian Catholic people during World War II.