You can find the details of Dasha's work below:

Mixed gender agreement in (one) Russian relative clause: two pilot studies

Wumbrand (2018) claims that in German, varying gender agreement in relative clauses is associated with two different types of anaphora. The mismatch example (1a) is only felicitous in the context of surface anaphora (The girl is the only girl), while the example without the mismatch (2b) involves deep anaphora with an abstract noun Ø(+ANIM). 

(1) a. Das...