"The principles of the Uranian system" 1971 by Hans Niggemann is an unauthorised translation of articles by  Carl Perch, Ludwig Rudolph, Herrmann Lefeldt and  Herbert Paules from German language into English language. All original sources were primaly published by our Witte-Verlag Publishing house.

pp. 1-3: "Short introduction to Uranian Astrology" author Carl Perch in HH 1/1962.
pp. 4-6: "Evaluation of Planetary Pictures" from introductory part "Rules for Planetary pictures" author Ludwig Rudolph
pp. 7-9: "Moon, nodes, Acendant, Aries point and Meridian in delineation" from introductory part "Rules for Planetary pictures" author Ludwig Rudolph
pp. 10-14: "The use of the disc"  from introductory part "Rules for Planetary pictures" author Ludwig Rudolph
pp. 14-23:  "Delineations of the Planetary Pictures" from introductory part "Rules for Planetary pictures" author Herrman Lefeldt
pp. 24-29: "Lesson 1"  author Carl Perch in the original called "1nd continuation (part 2)" in HH 2/1962.
pp. 30-38: "Lesson 2"   author Carl Perch in the original called "2nd continuation (part 3)  in HH 3/1962.
pp. 39-43: "Lesson 3"  author Carl Perch in the original called "3nd continuation (part 4)  in HH 4/1962.
pp. 44-45: "Combined Process of Investigation" author  Carl  Perch in HH 1965/3
pp. 46-50: "Lesson 4" is "Short Introduction to the Hamburger School - follow-up work" author Carl Perch in HH 1962/4
pp. 51-57):  "Showing the Development of a Chart of a Nurse" author Carl Perch: HH 1965/3, page 136
pp. 58-61: "Systematic Investigation of Actual Events" author Carl Perch in HH 1961/2, page 73
pp. 62-66:  "The Last of the Lessons"  author Carl Perch in HH 1965/2, page 67
pp. 67-74: "Description of Personality and Character from the Horoscope by Uranian Method" author Herbert Paules