Peter, G.: The genus Isostigma (Asteraceae, Heliantheae) in Paraguay, with a key to the species of the genus. — Willdenowia 34: 529–537. — ISSN 0511-9618; © 2004 BGBM Berlin-Dahlem.
The genus Isostigma, which is restricted in its distribution to eastern South America, ranging from Brazil to N Argentina, is revised for Paraguay and eight species are recognized to occur. I. herzogii is reported for the first time from this country (Dept. of Boquerón) and the presence of I. hoffmannii is confirmed (Depts of Boquerón and Chaco); both species are described and illustrated and their distribution is mapped. The other species in Paraguay are I. acaule, I. crithmifolium, I. dissitifolium, I. peucedanifolium, I. riedelii and I. speciosum. A key to all 13 species of Isostigma is provided.