That made it very difficult to certify a bill as being solely English.
Among the controversial provisions were changes to labor law for rail and airline workers -- backed by the airline industry -- that would count anyone who did not vote in an election for a union as voting against it, making it much more difficult to certify attempts to organize new unions.
Absolute values for DNA isolation procedures are difficult to certify, hence comparative results on community structures obtained using standardized ARISA with identical primers are of value.
Another issue is that the low-value, moisture-rich biomass flows that are being used are less homogeneous than the standardised, dry wood pellets that are being traded internationally, and therefore difficult to certify.
The following paragraphs explain why it is difficult to certify GNSS-based solutions for railway safety-related applications.
Despite this, ophthalmologists often found it difficult to ascertain when it is appropriate to certify patients, particularly for people with long-term conditions.
"We can't even certify exactly how many weapons the Pakistanis have — which makes it difficult to sound convincing that there's nothing to worry about".
"It obviously makes it difficult to shop".
"It makes it difficult to raise money".
It makes it difficult to say anything.
