Similarly, beginning with Oldrich Vasicek (1977), various short rate models, as well as the HJM and BGM forward rate-based techniques, allow for an extension of these techniques to fixed income- and interest rate derivatives. (The Vasicek and CIR models are equilibrium-based, while Ho–Lee and subsequent models are based on arbitrage-free pricing.) Bond valuation is relatedly extended: the Stochastic calculus approach, employing these methods, allows for rates that are "random" (while returning a price that is arbitrage free, as above); lattice models for hybrid securities allow for non-deterministic cashflows (and stochastic rates).