The articles about Short-toed Eagles in present southwestern /map/ and southeastern /map/ Poland are divided by about 80 years. Four of them, written by Viktor Zebe /map/ and published in the first half of the 20th century, have been placed on the Ptaki Śląska – Birds of Silesia website (De):
• Viktor ZEBE, 1933 – Beobachtungen an einem Schlesischen Schlangenadler-Horst [Observations on a Silesian Short-toed Eagle aerie] // Berichte des Vereins schlesischer Ornithologen, 18: pp. 47-57. – 
{rough translation}.
• Viktor ZEBE, 1935 – Weiteres vom Schlangenadler [More about Short-toed Eagle] // Berichte des Vereins schlesischer Ornithologen, 20: pp. 28-33. – {rough translation}.
• Viktor ZEBE, 1936 – Zur Biologie des Schlangenadlers (Circaetus gallicus Gm.) [Biology of the Short-toed Eagle] // Berichte des Vereins schlesischer Ornithologen, 21: pp. 33-78. – (translatable form).
• Viktor ZEBE, 1942 – Vom Schlangenadler, Circaetus gallicus (Gm.) 1936-41 [Short-toed Eagle within 1936-41] // Berichte des Vereins schlesischer Ornithologen, 27: pp. 2-10. – {rough translation}.
The next paper by Adam Flis is available on a website of the Institute of Nature Conservation PAS:
• Adam FLIS, 2013 – Występowanie gadożera Circaetus gallicus w Lasach Janowskich i Lipskich [The occurrence of Short-toed Eagle in Janowskie and Lipskie Forests (SE Poland)] // Chrońmy Przyrodę Ojczystą, 69 (3): pp. 221–225. – (Pl).