Zon question

How do deadly strike and critical strike add? I know I've seen an equation concerning this in the past, but I can't seem to find it now. I know they are not simply additive. I'm playing a bowazon that has 30% deadly strike from items, and I'm trying to figure out how much critical strike she would need, combined with the deadly strike, to give 100% chance for doing double damage. If some can direct me to the equation (X% CS + Y% DS = Z% chance for double damage) I will appreciate it. Thanks.|||http://classic.battle.net/diablo2exp/items/magic.shtml
About half way down.|||The simplified formula for your chance for double damage is
CS+DS-(CS*DS)
where CS and DS are expressed as percentiles, naturally (ie, 50% is 0.50)
http://diablo.incgamers.com/forums/showthread.php?t=693348&highlight=chance
And you can never get 100% chance for double damage unless you have 100% deadly strike. Zons usually shoot for L16 CS after all +skills, for 65% chance for CS. After that, returns diminish substantially.