This was mainly because contacts were difficult to be defined due to the young age of children, many children were in diapers, and practices followed by the personnel inside the kindergarten could not be accurately documented.
Non-point sources of traffic-related pollution become a major concern as they – compared to the point-source inputs – are more difficult to be defined or controlled.
Finally, more details on these lineages are presented in the legend of Figure 4; and the supporting data for the ancient lineages that are most difficult to be defined are presented in the Supplemental Text.
The generalized mathematical model uses uncertain parameters for content descriptors that are difficult to be precisely defined and measured, such as the level of intrusiveness and the change in performance over time.
Although mRNAs and their precursors are the only informational RNA class, their evolutionary transients are difficult to be thoroughly defined [5,53].
Task engagement is a difficult term to be defined but it can be recognized when it is around or missing.
For the logistic regression analyses, "I may be able to, but do not already do so" and "I think it is difficult to do so" were defined as "the athlete does not already do so".
One problem of defining behaviors as "risky" is that it is difficult to objectively define the risk with say, drinking and driving, or having unprotected sex.
Cameron's legacy is difficult to define because there is little that does define him.
