Post-cervical (pC) artificial insemination (AI) has been successfully developed for application in multiparous sows, although it has proved problematic in gilts.
Some institutions, like MoMA, have endeavoured to engage with this challenge by imagining the collection as "metabolic" (to use Barr's word) and constantly evolving, but it has proved problematic, and at times contentious, to shed works of art that have become recognized masterpieces in favour of the new and not yet fully appreciated.
The crested newt Triturus cristatus superspecies (Amphibia: Salamandridae), distributed in Europe and adjacent Asia, is an example of a relatively old, rapid radiation, for which it has proved problematic to obtain a resolved phylogenetic tree.
Although attempts have been made to measure appropriateness of attendance in terms of a categorisation of the processes of care (whether patients have received treatments/investigations/referrals or are admitted, for example), it has proved problematic to achieve consensus about what processes of care make a visit appropriate.
Dating the body has proven problematic, but it is thought that Lindow Man was deposited into Lindow Moss, face down, some time between 2 BC and 119 AD, in either the Iron Age or Romano-British period.
Application of the aphorism has proven problematic, particularly for anticipatory repudiations.
There are also notable cases in recent years when truly successful recasting has proven problematic.
Development of uniform recommendations for management of anticoagulated patients undergoing elective hand surgery has proven problematic.
For all the political schmoozing and promises of a "prime" future, being part of HQ2 has proven problematic.
Because such mechanisms also contribute to graft-versus-host disease (GVHD), separation of GVT effects from GVHD has proven problematic.
Putting the new variety into the hands of farmers, however, has proven problematic.
