message: Add reference to TACO.
diff: @@ -81,6 +81,9 @@ table QuantizationParameters {
  }
  // Sparse tensors.
  +// We use a modification of the TACO format.
  +// Reference: http://tensor-compiler.org/kjolstad-oopsla17-tensor-compiler.pdf
  +//
  // To encode a conceptual n-dimensional dense tensor with dims (d0, ..., dn-1),
  // potentially with a k-dimensional block (0 <= k <= n) with dims
  // (dn, ..., dn+k-1), the format needs to specify:
  