Revised translation of 'Analiticheskie svoistva diagramm Feinmana v kvantovoi teorii polia'. Sofiia: Izd-vo Bolgarskoi Akademii Nauk, 1966.
Analytical properties of Feynman diagrams in quantum field theory by I. T. Todorov. ISBN 0080165443. Published by Pergamon in 1971. Publication and catalogue information, links to buy online and reader comments.