That's a great find, Rob!
Three Dog Night ruled (at least) the North American part of the Earth in the late 60ies and early to mid 70ies and then basically vanished off its face without too much noise. I've often asked myself why, and my pet theory of an explanation is that they didn't write their own songs - a self-penned body of work seems to be key regarding the longevity of remembrance of a band in the public mind. Interestingly, that doesn't seem to apply to solo artists, Elvis Presley, Tom Jones, Aretha Franklin, Tina Turner, Celine Dion - who cares that they mostly sang other people's songs? But if you're a rock band and do mostly or only covers, irrespective how well and original you do them (---> Manfred Mann's Earth Band), you are automatically relegated to the "not-to-be-taken-quite-so-serious-as-a-creative-force"-bin. It's the reason why bands like The Beatles, The Rolling Stones, The Who, The Bee Gees and The Kinks all have gained - especially as the 70ies approached - a different status than, say, The Hollies.