Petrick: 7 X Petrick (Blue) © Petrick (Petr Krejcik), Praha, CSSR Softcover, saddle-stitched, 6x8.5", 13 pages

Image from Magicref

Comments: Effects with Balls. Blue cover with 7 of clubs and a hand holding three balls. In English and German.
The Seven by Petrick Series were released in seven volumes, each with seven tricks, and each with a different color cover and topic covered. The others were:
7X Petrick Red with 7 of Hearts - Cards
7X Petrick Green with 7 of Clubs and a Handkerchief - Silk magic
7X Petrick Orange with Joker - Cards
7X Petrick Black with 7 of Spades - Cards
7X Petrick Maroon with silhouette of Petrick Throwing a Ball - Stage Magic
7X Petrick Purple with silhouette of Petrick's profile - Miscellaneous Magic

Contents (Andrew Pinard, and book):

1 Production of large ball from previously empty top hat
3 Production of six balls from a shawl
5 Produced ball disappears from the enclosure of a scarf
7 Color-changing ball with scarf
9 Color-changing balls through tube
11 Vanishing large ball from top hat
13 Floating large ball