I grow a number of these, though not the two species you mention.
rareplants.co.uk offer a few most years (they currently offer baissunensis) and forumist Jan Jilek offers a lot of them though I've never bought from this source.
The ones I grow are perfectly cold hardy (biflora, tschernjaewi, petiolulosa, plus several similar yellow 'species') but do need a dry summer rest so I keep them under glass here - this may not be necessary if you have a dry summer climate. I find them reasonably easy, though biflora is trickier than the others. They are watered on a typical 'bulb' schedule - a good watering in autumn and then kept just moist until growth appears - this is as early as January for some. They are then watered freely until May and then dried off for the summer.
I'm certainly no expert on them but I can keep them going, so a couple of years back I was persuaded to write about growing them for the Edinburgh SRGC group newsletter. As a result of this an expanded version of the article has just been submitted to the SRGC journal.