This form was described very little in several old books. It's quite confusing, because some decribed it as Lilium martagon var. pomponium and also Lilium pomponium. Also it is described in a general area from Burgos "in Burgos Mountains" or "near Burgos city". This is quite impossible to imagine because there is just one environment where this variety could grow near Burgos city, but it hasn't got enough altitude.
All locations of Lilium pyrenaicum in "Atlas de la Flora de Burgos" are the typical yellow form , and all my botanist friends and botanic photographers have never seen it. As you can see there is just one picture of this variety and is not from the nature. It is very strange that nobody has ever taken a picture of it, maybe it was completely extinguished due excesive extractions.
But I know a place in Burgos where Lilium pyrenaicum and another Lilium from different color I remeber orange-pink are blooming at the same time, and that is not marked in the Atlas of Burgos. I think it could be Lilium pomponium. It is near a medieval church from XII century and it seems there is a relation with this profusion of Liliums and the church as it has stone work decorations about Lilium.
I will see in spring this place, to know if thi Liium sp, is just a Lilium martagon or another species.