Board Thread:Policies/@comment-867021-20130305115037/@comment-3406131-20131030174310

Personally (but I'm no admin), I always fill up the field with "-", as I consider that the apn is also here to follow series with different names, as for Kitty Pryde in her back to Chicago period (haven't finished, will do later the end): She "start" (haven't done the beginning as the appearance category is bugging because that character has more than 500 appearances) in, then continue in some other issues, and finally end up in Mekanix. Since she is in Mekanix for the whole series, there is no need to precise in the first issue she will be present in the second issue, because:
 * It make believe that she won't, before you look the link
 * If we say in the first issue that she will in the following ones, it would be logic to add it for every issues, and we're not going to do it.

Idem for the previous.

So my opinion would be: It's either an issue reference or a "-", but never leave a blank.