I'm having a hard time finding articles on "qualified plurality runoff" elections. That is, elections in which there is a second-round runoff, unless there is a specific distance between the first and second place winners and/or the first place finisher exceeds a certain threshold (say, 40%). Can anyone point me to some? I've checked Google Scholar and various other places, but can only find a handful, and mostly older. Recently, many countries in Latin America adopted qualified runoffs, and I'm sure there must be some papers about them. Thanks.