current - Operational Transconductance Amplifier Input Configurations

I recently purchased several OTAs (Lm13700) but have had quite a bit of trouble using them. Going through the TI datasheet and a Nuts & Volts tutorial it's occured to me that transconductance amps don't really function in the same manner as "normal" op amps. Excluding the obvious currrent output in place of a voltage output the input configurations for many of the example circuits I've seen don't seem to follow normal op amp rules. Most pointedly, while I understand that hysteresis isn't a problem thanks to controllable gain I don't understand why so many circuits feature resistors attached to both input pins. It would seem to me that to achieve differential voltage gain one simple had to apply a voltage to the non-inverting input (perhaps with a voltage divider) and tie the other to ground. However, I tried this on a breadboard without success and only one circuit I found actually suggested this. Would someone mind explaning why OTA amplifier circuits differ so radically from ordinary op amps?