Previous B.P.R.D. title is the five-issue series B.P.R.D., Plague of Frogs (Dark Horse, 2004 series). Next is the six-issue series B.P.R.D., The Black Flame (Dark Horse, 2005 series). Starting with the first issue of this series, inside front covers of B.P.R.D. one-shots and miniseries include the note "Number X in a Series" counting from BPRD: Hollow Earth [B.P.R.D.: Hollow Earth] (Dark Horse, 2002 Series) #1.
Indicia title has comma (as indexed) rather than colon.