Despite how nearly half of the late Donna Summer's studio albums are off the market, the diva's catalog is due to make waves on the Billboard charts next week.

Donna Summer: In Memoriam -- There Will Always Be a You

Sources say her seven currently available greatest hits albums, along with a remix collection, could collectively sell between 20,000 to 40,000 copies by week's end on Sunday, May 20. (Up from less than 1,000 last week.) The biggest seller of the bunch might be The Journey: The Very Best of Donna Summer, which was released in 2003. Also performing well is her first best-of, 1979's On the Radio - Greatest Hits Volumes I & II.

However, there are a number of albums that are certain not to appear on any of our charts next week: Her five releases with Geffen Records and two for Atlantic Records in the 1980s and 1990s.

Donna Summer Dominates Social Networks After Death

Why? All seven of those titles are out of print -- both physically and digitally -- and are owned by Summer's estate. They include Geffen's The Wanderer (1980), Donna Summer (1982), Cats Without Claws (1984), All Systems Go (1987) and I'm a Rainbow (a shelved album from the early 1980s that was unreleased until 1996).

For Atlantic, she released Another Place and Time in 1989 (which includes the top 10 Billboard Hot 100 single "This Time I Know It's For Real") and Mistaken Identity in 1991.

Radio Remembers Donna Summer: Songs Get Huge Airplay After News of Singer's Death

Her Geffen albums have been unavailable since 2003, while Atlantic's Mistaken Identity and Another Place and Time left the marketplace in 1996 and 2009, respectively.

Summer recorded for many labels in her career, aside from Geffen and Atlantic. The bulk of her material was released through Casablanca Records from her first U.S. album in 1975 ("Love to Love You Baby") through the hits set Walk Away in 1980. While most of her Casablanca sets are available via digital services, not all are still available as physical albums.

Donna Summer's Enduring Billboard Chart Successes

After departing Casablanca, she released two Geffen albums in 1980 and 1982, and then issued She Works Hard for the Money for Mercury Records in 1983. While that album can be found digitally on iTunes and in other e-tailers, it's been out of print as a CD since 2003.

After parting ways with Atlantic in the early '90s, she moved on to Epic Records for 1999's concert set Live & More Encore.

Tributes For Donna Summer: Gloria Gaynor, Neil Portnow, Nile Rodgers, More React

Her final studio album released in her lifetime was 2008's Crayons, issued through Sony Music's Burgundy Records. It debuted and peaked at No. 17 on the Billboard 200 and is still currently on the market -- both physically and digitally.