Despite this, the recent evolution of many new and differing standard schemes is considered a major obstacle, creating difficulties for project developers and buyers to select appropriate standards.
The root-derived carbon (C) input to the soil, whose quantification is often neglected because of methodological difficulties, is considered a crucial C flux for soil C dynamics and net ecosystem productivity (NEP) studies.
The criterion-referenced test, which was applied in the present study, aims to measure the level of achievement of respondents against given goals or standards, thus an item with non-discrimination against a higher difficulty index is considered a better achievement of instruction measured by the item [ 18].
The presence of learning disability was excluded based on information provided by parents and schools during the clinical and cognitive assessments, or by the presence of significant discrepancies between verbal and performance intelligence quotient (IQ) subscores, which is considered an indicator of potential learning difficulties.
Inter-cultural differences were considered a source of difficulties in discussing prenatal or preconceptional screening.
Not being able to "work through" a stage was considered a sign of psychological difficulty and therapists were encouraged to help people pass through each of the "phases".
At the time it was considered a prime example of the difficulty of Tech's curriculum, and referred to in jest by students as "Drowning 101".
Schools with facilities for special needs education (e.g., for children with learning difficulties) were considered a special case and not included for reasons of homogenous sampling.
For example, in Cheng et al.'s original publication, HIV integrase was considered a difficult target based on the difficulty in finding inhibitors over many attempts.
The analysis of the dissolved organic fraction of hydrothermal fluids has been considered a real challenge due to sampling difficulties, complexity of the matrix, numerous interferences and the assumed ppb concentration levels.
