Can I post recipes at bulletin board service?

Dear Rich: I have a “bulletin board” web service limited to subscribed members with a special medical problem. I make no money from the board. Often, recipes are posted which are intended to facilitate the treatment of the medical condition. Often these recipes are copied, or at least derived from recipes probably taken from commercial cookbooks or from the web. Sometimes they are attributed, at least by a link, and sometimes they are not. Can I be held responsible for furnishing the service by which these recipes are disseminated? The law states that the recipe’s author’s description of the technique used to assemble and cook the item is subject to copyright. My pile of cookbooks are literally filled with recipes that are indistinct from one book to another, and websites are filled with recipes indistinct on multiple sites. I intend to add to my "Information for New Subscribers" this instruction: “When possible, recipes that are copied from a recipe book or website should be attributed, or a link provided to the website from which it was taken.” Is this sufficient to cover me? I should add that the purpose of the board is not to post recipes, but to also share support, advice, and resources.  Speaking of recipes, let's start with a shout out to the Dear Rich staff for their excellent red pepper tapenade recipe. (It's pretty close to this recipe except without the garlic, of course) By the way, we've discussed recipes before and we think this post and this post address many of your concerns. In general, you're probably fine operating in the manner you described. You rarely need to be concerned about copying one or two recipes from a cookbook. But you should be concerned when a bunch of recipes are copied from one source. In that case, you're more likely to hear from the copyright owner who may claim that their collection or "compilation" has been infringed.
What should your notice say? We think your Terms and Conditions (to which each member of your group should agree before joining), should include a statement to the effect of: "We don't permit the posting of materials that infringe copyright or violate the law and we reserve the right to remove such materials." That's pretty general but it sets the tone in case you are asked to remove materials. FYI, attribution and linking are fine but keep in mind that they won't get you off the hook for infringements.