Romer (1986): Increasing Returns to Long Run Growth
Lucas (1988): On the Mechanics of Economic Development
Romer (1990): Endogenous Technological Change
Jones (1995): Time Series Tests of Endogenous Growth Models
These are all classic papers in this vein of endogenous growth and questions of cross-country convergence/divergence.
When you are using implicit differentiation along a level curve you will treat the variable with respect to which you are differentiating as a single variable, rather than function. This is because the formula for implicit differentiation along level curve is already based previous derivation where you already solve for $y'$.
For example, for general ...