help on AAC papers on AES

Hi all
	I'm new member in this group and currently doing the AAC LC encoder.
Since I am not a member of AES, could you share the following papers
with me if you have? Also I want to make clear the following conceptions
on AAC:

1. Is there any difference between MPEG2 AAC LC and MPEG4 AAC LC besides
the PNS tool?

2. Should MPEG4 AAC be backward compatible with the MPEG2 AAC?

3. I always hear somebody said about AAC LC profile or LTP profile. But
according to the MPEG4 standard, AAC LC and AAC LTP are two audio object
types. MPEG4 defines eight profiles for each audio object type. For
example, it defines scalable audio profile, main audio profile, high
quality audio profile and natural audio profile for AAC LC audio object.
So what's the difference for each profile?
	Thanks

Kevin
	M. Bosi, K. Brandenburg, S. Quackenbush, L. Fielder, K. Akagiri, H.
Fuchs, M.

Dietz, J. Herre, G. Davidson, Y. Oikawa: "ISO/IEC MPEG-2 Advanced Audio
Coding",

Journal of the AES, Vol. 45, No. 10, October 1997, pp. 789-814
	J. Herre, D. Schulz: "Extending the MPEG-4 AAC Codec by Perceptual Noise

Substitution", 104th AES Convention, Amsterdam 1998, Preprint 4720
	D. Schulz,

"Improving Audio Codecs by Noise Substitution", Journal of the AES,
Volume 44,

Number 7/8, July/August 1996, pp. 593-598