Riddles have been part of the folklore of the Yugoslav nations since very early times, and the first were written down at the beginning of the sixteenth century. During the nineteenth century, riddles appeared regularly in literary magazines and collections of folk riddles were published. The first modern crossword puzzle appeared in Zagreb on March 1, 1925.
"Yugoslav Puzzle Periodicals,"
Word Ways: Vol. 11
, Article 2.
Available at: http://digitalcommons.butler.edu/wordways/vol11/iss4/2