If it is impossible to obtain the data, the study will be excluded from the data synthesis.
However, it is often impossible to obtain LiDAR data of permanently inundated river beds.
Moreover, cognitive impairment makes it difficult if not impossible to obtain interview data from a patient.
It would be difficult and essentially impossible to obtain reliable data for the comparison of different samples on different gels.
Unfortunately, the stomach cancer patients had succumbed to their disease and it was impossible to obtain mutation data from any of them.
The limitation of our study is the retrospective design, which made it impossible to obtain reliable data about motor function at follow-up.
Representative information on the pattern of disease in the general canine population is impossible to obtain from data studies utilizing secondary (referral) centres, because of the well-recognised "referral bias" [ 1], owing to variables including geographical location and wealth of owners.
We did not, therefore, include this variable in our analysis, nor did we include practice size because it was impossible to obtain these data for individual physicians in our samples, and because practice size was not a significant predictor of job satisfaction in another study that controlled for autonomy and other physician and practice characteristics (such as perceived time pressure) [ 20].
Because a combination of factors-cost, reliability, uniformity and convention-made it virtually impossible to obtain historical options data, we developed a data-flow system to capture, process and analyze streaming data over a period of over a year.
