HOLLYWOOD (Variety) - For the fourth straight week, teen idols 'N Sync retained the top spot on the national music charts as "No Strings Attached" (Jive) sold more than 422,000 copies, according to sales data released Wednesday.

'N Sync's sales for the week ended April 16 were more than double that of runner-up No Doubt's "Return Of Saturn" (Interscope), which moved nearly 202,000 units and garnered top debut honors for the alt-pop outfit's first release in five years.

Femme rapper Da Brat's "Unrestricted" (Columbia) was the week's other significant debut, coming in at No. 5 with more than 143,000 copies sold.

Top sales increase of the week went to singer Christina Aguilera, whose eponymous first album (RCA) was up 8,000 copies over its previous week's figures.

Other significant sales gainers were rock group Creed's "Human Clay" (Windup) -- up 7,000 copies; rapper Jay-Z's "Life and Times of S. Carter" (Rock-A-Fella/Def Jam); the various artists' two-CD Christian compilation "Wow Worship Orange" (Integrity/Word/Epic); and singer-songwriter Joni Mitchell's "Both Sides Now" (Warner Bros.), all of which were up 6,000 units.

Universal captured the largest share of the week's current album market, 27.5%, followed by BMG, 19.7%; Sony, 16. 9%; Warner, 13%; and EMI, 7.7%.