It is difficult to determine when the notion of soul first emerged in Jewish writings.
Because some former plant workers have become cleanup workers, it is difficult to determine when they were exposed to the toxic substances.
It's difficult to determine when a wine reflects the intentions of a winemaker, and when it expresses the characteristics of a region.
Of course, it is sometimes difficult to determine when to pull the plug on a company, said a former senior executive of the online retailer Boo.com, which shut operations in May, and recently re-opened under new ownership.
The Civil Aviation Authority, a safety regulator, said that weather conditions were making it difficult to determine when flights might resume even as the volcano continues to erupt, although at a lower intensity.
Lawyers for the city, who conducted the review in response to a court order to sort out the seriousness of the claims, also found that many records were contradictory or incomplete, making it difficult to determine when an ailment began or how long it persisted.
After 20 years of free trade between the United States and Canada, Jayson Myers, the president of Canadian Manufacturers and Exporters, an industry group, said it was sometimes difficult to determine when something was an American product or a Canadian one.
Despite years of experience, it was often difficult to determine when to medicate.
However, it was difficult to determine when adjuvant S1 treatment was finished.
The effects of these processes are especially difficult to determine when they occur quickly and simultaneously.
