This article mentioned here in 2006 is available online now:
• Graham R. MARTIN & Gadi KATZIR, 1999 – Visual Fields in Short-Toed Eagles, Circaetus gallicus (Accipitridae), and the Function of Binocularity in Birds // Brain, Behavior and Evolution, 53: pp. 55-66. – 
(En).
Some other articles on the ResearchGate portal will be represented here soon.
The following two texts are dedicated to notable physical abilities of Short-toed Eagles and
, like the previous one of Bernard Joubert, are going to be included in the next issue of La Plume du Circaète (Fr):
• Bernard JOUBERT, 2015 – Performance visuelle du Circaète [Visual abilities of Short-toed Eagle] // short-toed-eagle.net.
• Bernard JOUBERT, 2015 – Quelques réflexions sur le vol [Some reflections on the flight] // short-toed-eagle.net.
This is just selection of links on miscellaneous texts and abstracts of articles about Short-toed Eagles. So…
Some abstracts can be found on the NCBI website with PubMed database:
• Sacchi P, Soglia D, Maione S, Meneguz G, Campora M, Rasero R, 2004 – A non-invasive test for sex identification in short-toed Eagle (Circaetus gallicus) // Mol Cell Probes, Jun 18 (3): 193-6. (En).
• Martin GR, Katzir G, 1999 – Visual fields in Short-toed Eagles, Circaetus gallicus (Accipitridae), and the function of binocularity in birds // Brain Behav Evol, 53 (2): 55-66. (En).
The encyclopedic compilation of information (Es) among other things has extensive ornithological bibliography concerning researching of Short-toed Eagle. The source is a site of the Enciclopedia Virtual de los Vertebrados Españoles.