Which versus That

[Jaggers]

Any views on which of the following is better (and why)?

(a) I was reading the guidelines which were really helpful to my understanding of the problems.

(b) I was reading the guidelines that were really helpful to my understanding of the problems.

 

[5jj]

If you were reading only the helpful quidelines, then there is no difference between those two. If you read all the guidelines, and found them helpful, then only the following is correct:

I was reading the guidelines, which were really helpful to my understanding of the problems.

 

[Jaggers]

Many thanks indeed, I somehow overlooked that "the guidelines that were really helpful" might be a subset of all the guidelines. Noted about the comma!