Complex sentence: In spite of Aaker and Keller's (1990) research which reports that prestigous brands are not harmed from failure of extensions, some evidence shows that the dilution effect has great and instant damage to the flagship product and brand family.
Split into simpler sentences: In spite of Aaker and Keller's (1990) research reported that the prestige brand do no harm from failure of extension. Evidence shows that the dilution effect has great and instant damage to the flagship product and brand family.