Levinski+Magidor+Shelah, Chang's conjecture for $\aleph_ \omega$ -- Israel J Math 69 (1990) 161-172.
See also "Some consequences of reflection on the approachability ideal" by Matteo Vilale, Assaf Sharon, Transactions of the American Mathematical Society 362, 4201-4212, 2009. In particular fact 4.2 and remarks after it.