* Devil's Lake (1973)
* Wagon from the Grave (1974)
* Mark of Power (1976)
* Fire Signs (1978)
* Sign of Light (1979)
* The Sign of Water (1980)
* Vindens tegn (1981)
* Mark of the Earth (1982)
* Tidens tegn (1983)
* Space Sign (1984)
* Livstegn (1985)
* Death Note (1986)
* Sign of Love (1987)
* Mark of Hate (1988)
* Mark of Betrayal (1989)
* Sign of Victory (1990)
* Mark of Defeat (1991)
* Sign of the End (1992)
* The Sign of the Beginning (1993)
* Mark of Rebirth (1994)
* Sign of Hope (1995)
* Troens merke (1996)
* Sign of Love (1997)
* Mark of Hate (1998)
* Mark of Betrayal (1999)
* Sign of Victory (2000)
* Mark of Defeat (2001)
* Sign of the End (2002)
* The Sign of the Beginning (2003)
* Mark of Rebirth (2004)
* Sign of Hope (2005)
* Troens merke (2006)
* Sign of Love (2007)
* Mark of Hate (2008)
* Mark of Betrayal (2009)
* Sign of Victory (2010)
* Mark of Defeat (2011)
* Sign of the End (2012)
* The Sign of the Beginning (2013)
* Mark of Rebirth (2014)
* Tegn på håp (2015)
* Troens merke (2016)
* Tegn på kjærlighet (2017)
* Mark of Hate (2018)
* Mark of Betrayal (2019)
* Sign of Victory (2020)
* Tegn på nederlag (2021)
* Sign of the End (2022)
* Noveller
* The Black Box (1970)
* Deathtrap (1971)
* Devil's Eye (1972)
* Hell's Gate (1973)
* Fire from Heaven (1974)
* Dødens vann (1975)
* Wind of Destruction (1976)
* Jordskjelv (1977)
* Shadow Government (1978)
* Invasjon fra verdensrommet (1979)
* The End of the World (1980)
* Faglitteratur
* Hemmeligheten bak pyrene