Error when 2 citations have same author (without parenthesis)

[JVAQUEROM]

Describe the bug
Problem is that if I try to cite the same author (different papers) twice, like @Doe2015 and @Doe2016 y get "Doe et al. (2015) and Doe et al. (2016)". But I want "Doe et al. (2015, 2016)".

To Reproduce
Take two works of the same author and cite them togeter WITHOUT parenthesis. You get @Doe2015 and @Doe2016

Expected behavior
Pandoc requires that you write this as @Doe2015 [@Doe2016].

Additional context
You can take a look at original issue ismayc/thesisdown#153