Complex sentence: Originally published biannually, Bookforum became a quarterly in 1998, and since 2005, the magazine publishes five times a year, with issues coming out in February, April, June, September, and December.
Split into simpler sentences: Originally published biannually, Bookforum became a quarterly in 1998. Since 2005, the magazine has been published five times a year, with issues coming out in February, April, June, September, and December.