Jake Ivan (Colorado Parks and Wildlife) has recently worked up a chapter on the 'density estimation' data type in MARK. While still in 'late draft' stage of development (meaning, the chapter is likely to change with some frequency over the next few weeks), I put said draft online on the MARK book website (chapter 20). The data files Jake refers to are also available in the usual markdata.zip archive.
I'd like to thank Jake for his contribution.