Should article "the" be used?

Good day! I don't catch if it is strictly necessary to put a definite article if the noun has already been mentioned. Like here:
"Good methods to do this are listed here. Good methods to do this also include...".
I was told that while not using "the" in such sentences, it means we are talking about some of the methods, not an exhaustive list. Is it correct? And is it strictly necessary to put "the" in the second sentence? If yes, will it still mean those "some of the methods" I was talking about in the first sentence. Thanks!