Unfortunately, plants of northern Chilean provenance of this species have proven difficult to cultivate in a variety of settings in the USA.
"So we're not necessarily relying on the partnerships that have proven difficult".
SUMMARY: A group of special interest to mammalogists, taxonomists, and systemicists, ungulates have proven difficult to classify.
Those cuts have proven difficult to implement, as have promises to eliminate Amtrak subsidies and cuts to food stamps.
That would seem to be an easy win for us, but TFC have proven difficult for us in the past.
Its cowboy culture and internal politics have proven difficult to rein in, and its sheer size makes it hard to move the profit needle.
Cereal agriculture is heavily mechanised, with one combine harvester taking over from hundreds of labourers, but other tasks have proven difficult to automate.
Reforms in that direction have proven difficult.
However, efficient admissible heuristics have proven difficult to find.
Additionally, some biopharmaceuticals such as antibodies have proven difficult to express at high levels.
But larger OLED screens have proven difficult to manufacture due mainly to cost and reliability constraints.
