Natascha Müller's article concerns the acquisition of word order in German subclauses by young bilingual children. Müller's basic argument as I understand it runs as follows:
(1) In the acquisition of word order in German subclauses some children make errors and others do not;
(2) there are some monolingual and some bilingual children who do not make errors;
(3) there are some monolingual and some bilingual children who do make errors, and the errors are qualitatively similar for monolingual and bilingual children;
(4) when children do make errors, they occur more frequently in bilingual than in monolingual children;
(5) the errors in both monolingual and bilingual children are due to the misprojection of a separate functional category;
(6) in addition, the errors in bilingual children (but not in monolingual children) are due to influence from the other language they are simultaneously acquiring. The reason for positing this is that bilingual children's errors are more frequent than monolingual children's errors.