[to do sth; at doing sth; of doing sth
It is also clear that there are extensions to......, but they do not seem to be worth the effort of formulating them separately.
In an effort to generalize Robert's method, we gave in [2] the following criterion for non-finite generation of kernels.
The first of these was suggested by J. Serrin, who showed how to modify my earlier treatment of...... so as to obtain stronger results with no extra effort.