[see also: complication, trouble, issue, subject, matter, topic, point
The main problems that we address are......
However, we immediately encounter the problem of nonregularity of the data.
In the final section of the paper, we list some open problems.
To overcome this problem, we revise our definition of a branch.
We can now pose a problem whose solution will afford an illustration of how (5) can be used.
The problem one runs into, however, is that f need not be......
The problem is to move all the disks to the third peg by moving only one at a time.
However, even for k=1 the problem proved quite difficult.
The factor Gf poses no problem because......
Pointwise convergence presents a more delicate problem.