Looks good; but ref. 5 really needs to be replaced with a better source (ref. 4 is not too bad).
"In contrast with modern, succinct notation like y=x;, COBOL uses MOVE xTOy." - Should be something like: "COBOL uses more traditional notation [or "more English-like notation", whichever fits better] (in this case, MOVE xTOy)". And shouldn't it be "syntax" instead of "notation"?
"A 1959 survey had found that in any data processing installation, the programming costs at least $800,000 and that translating programs to run on new hardware would cost $600,000." - correct grammar in underlined text (suggestions above). Also, the source says the cost is on average, so I think it should mention that the cost is on average.
"In the early 1990s it was decided to add object-orientation in the next full revision of COBOL. - should be reworded.