The circuit uses the two OP amplifiers (TL082). The OP of the one works as the Schmitt circuit. The other OP works as the integration circuit.
http://www.hobby-elec.org/e_ckt16.htm
circuit generates frequency-locked triangle waves of constant amplitude, uses readily available TTL and other older-technology parts
http://www.edn.com/archives/1998/020298/03di_01.htm
uses common 1458 dual op-amp
http://ourworld.compuserve.com/homepages/Bill_Bowden/page8.htm#func.gif