• Three Ways to Express Future Events
(1) present continuous: Emphasizes the present effect of the future event. Fixed plans. (2) be going to: Emphasizes the intention. Plans made in the past. (3) present simple: Future event based on a schedule or timetable. Used in subordinate clauses.
http://qindex.info/i.php?x=4068

• Be Going To
(1) future plans decided before "I can't go with you tonight I'm going to study at the library with some friends." (2) predictions we can see now "Look at the clouds! It's going to rain."
http://qindex.info/i.php?x=4134

• Be Going To
(1) future plans decided before "I can't go with you tonight I'm going to study at the library with some friends." (2) predictions we can see now "Look at the clouds! It's going to rain."
http://qindex.info/i.php?x=4973

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