I realize the term 'Advanced Calculus' is rather vague, so to be more specific I'm looking for a textbook covering multivariable analysis. I've taken a look at Shifrin's Multivariable Mathematics and Hubbard and Hubbard's Vector Calculus, Linear Algebra, and Differential Forms, and these seem like quite nice books. However, I'm concerned that they may be less than rigorous. What does everyone think of these books? In addition to these, what other (potentially more challenging) books are recommended?