& Paulus, H. F.
Untersuchungen zur Morphologie, Taxonomie und Phylogenie der Chelicerata. Zeitschrift für zoologisches Systematik und Evolutionsforschung, 17, 85-116, 177-200.
This is one of the classic studies of arachnid phylogeny, the first cladistic model, and was widely accepted until the advent of Shultz's (1990) scheme. Significantly these authors included aglaspids in Chelicerata and regarded scorpions as the most primitive arachnids. The other arachnids were then broadly split into those with book-lungs (Megoperculata) and those lacking book-lungs (Apulmonata). Though not without it's weaknesses, many of these author's characters have been adopted by subsequent workers.