1. N.S. Choi and J. Heller, Drug delivery devices manufactured from poly(esters) and poly(ortho carbonates), US Patent 4,093, 709, June 6, 1978.
2. N.S. Choi and J. Heller, Structured orthoester and orthocarbonate drug delivery devices, US Patent 4,131,648, December 26, 1978.
3. N.S. Choi and J. Heller, Erodible agent releasing device comprising poly(ortho esters) and poly(ortho carbonates), US Patent 4,138,344, February 6, 1979.
4. N.S. Choi and J. Heller, Novel orthoester polymers and orthocarbonate polymers, US Patent 4,180,646, December 25, 1979.
5. J. Heller, D.W.H. Penhale and R.F. Helwing, Preparation of poly(ortho esters) by the reaction of diketene acetals and polyols, J. Polymer Sci. 18 (1980) 619–624.