General Comments
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As before, I correct grammatical errors or I reword sentences. All my
changes are in bold.

On some occasions you use low-redshift and other occasions you use low
redshift, without the hyphen. You should choose one or the other but not
both.

Similarly, you might want to be a bit more consistent with the way
low-redshift SNe are descirbed. In the paper, you have used local,
nearby and low-redshfts as adjectives to describe the same thing.

Answer: I have put them all to low-redshift.
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Abstract
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If the two SN1991T-like SNe in Matheson et al. have been correctly 
identified, then the following is no longer true.

"making it the first object of this type identified at high reshift."

There are other similar sentences in the text which might have to 
be removed or modified.

Answer: I've removed it. 
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Introduction
============
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The word "alternative" in the second paragraph implies that one alternative
has already been discussed, which is not the case. You can either drop
the word or move the discussion about lightcurve tests for homogeneity
from paragraph 3 to paragraph 1.

Answer: I've added the following sentence in the first paragraph.
"this implies testing that type Ia SNe do not evolve with redshift."
and dropped the word "alternative"
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The following sentence seems to be incomplete.

"For example, attempts have been made to compare light curve parameters
but \citep{1999AJ....118.2675R,2000AJ....119.2110A,2001ApJ...558..359G}."


Answer: changed in  "As
of now few attemps have been made to quantitatevly compare supernovae
propierties at different redshifts and only based on light curve
parameters
\citep{1999AJ....118.2675R,2000AJ....119.2110A,2001ApJ...558..359G}."
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Section 2.2
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I removed the word "possible" from

"possible spectral peculiarities among SNe~Ia"

I do not understand comment "f" - "In Normal Ia typical line profile
time evolution."



Answer: I've replaced the word typical with characteristic. I mean that the line profile time evolution for type Ias is unque among SN, and thuse it is a distinctive chraracteristic of Ias.
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Section 3.2
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Instead of

"Equivalent width ({\sc ew}) time evolution measurements have been
empirically shown to be excellent means to study the spectral homogeneity
of SNe~Ia and to provide reliable indicators of SN~Ia intrinsic brightness
\citep{folatelliew}."

I suggest

"Equivalent widths can be used to charactrise the spectral homogeneity
of SNe~Ia and to measure their intrinsic brightness\citep{folatelliew}."

I think that we should not use the word excellent in this sentence as
Gaston's paper has not been accepted (or even submitted). :(

Answer: I agree.
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In the second sentence, I replaced "signs of evolution" with
"differences" since any observed diffrence may be due to either
evolution or selection biases that affect low and high redshift SNe
differently.

Answer: Right!!
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Why was SN 2002gi not measured. Was the S/N ratio too low? 

Anser: Yep!!
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You might need to describe inmore detail how the shaded region
in figure 7 is defined.

Answer: I 've changed the sentence to "Instead, {\bf the
portion of the plot where most low-redshift normal and under-luminous
SNe are located is indicated}, for clarity, by a gray-filled
region.". I'm not sure if now is more clear but the bottom line is I basically colored of gray the region where most of the SN lay. There is no statistical meaning in the gray-region only a presentation issue. 
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In figures 5,6,7, you might need a sentence to explicitly state that
the large symbols represent the high-z SNe.

Answer: I've added High-redshift supernova are indicated by large
symbols. in the caption
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Section 3.3
===========



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Since the table describes the columns adequately, the following 
senetences are probably unecessary.

"The first two columns of Table~\ref{emdata} {\bf reports the
$\chi^{2}$} refer to the comparison with the `Fe~{\sc ii} 4800' and
`Mg~{\sc ii} 4300' {\sc ew} models for normal supernovae. The last two
columns refer instead to the comparison with under-luminous SNe
(e.g. SN~1986G \citep{1987PASP...99..592P} and SN~1991bg)."

I think that you need to give reasons why the mean value of the EW of
the `Mg~{\sc ii} 4300' feature for high-redshift SNe~Ia is, on
average, higher than the mean trend set by local SNe~Ia. Are we
detecting some sing in the evolution, could it be a systematic effect
caused by biases in the selection and/or analysis, or could it be that
the sample size is just too small.

Answer: I now re-write the sentence as "However, note that the {\sc ew} of the
`Mg~{\sc ii} 4300' feature for high-redshift SNe~Ia is, on average,
higher than the mean trend (all the points are however included within
2-$\sigma$), especially before maximum light {\bf reflecting in the
relatively large value for the $\chi^{2}$. This could be due to a
residual systematic effect in the host galaxy contamination
subtraction. In order to understand if this 2-$\sigma$ effect could
instead being pointing toward evolution a larger dataset
should be included in the analysis.}"
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Table 3
=======

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The following sentence is a bit vague.

"However, this assumes ideal conditions."

You should consider removing it.


Answer: I've removed it
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---

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I have two concerns about the following paragraph.

\citet{2000ApJ...530..966L} claim that the strength of supernova
absorption features should be affected by the drift toward lower
metallicity progenitor expected at high-redshift. However, measuring
the intrinsic spread of {\sc ew}s of the absorption features of their
models relative to those of the one solar metallicity synthetic
spectrum, we found values lower than what is measured on the local
supernovae. Thus, the range in which {\sc ew} vary -- studied in
\citet{folatelliew} -- is dominated by other effects than their
prediction from metallicity variations. The possible change of
rest frame U-B color in high-redshift SNe is probably a more sensitive
parameter to investigate the effects of varying metallicity.

How good are the models? Might it be that the models are not
accurate enough. You dismiss metallicity as a possible cause for the
measured intrinsic variation, because you measure a small variation
in the models. If the models are not very accurate, then this might
be not be the correct conclusion.

ANswer: I meant this concern being included in the sentence "is
dominated by other effects than ***their*** prediction from metallicity
variations". IF you think this is not enough we can rephrase putting a stronger warning sign.
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Since this paragraph discusses only the local SNe, perhaps it should
appear in Gaston's paper. However, I have not seen any progress in Gaston's
paper in the past six months, so I do not strongly believe that it should be
removed. Nevertheless, you may want to modify it after considering my first
point.

Answer: I think we need to state it here since it is of interest for high redshift SNe.
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Section 3.4
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Some of the numbers seem to be a bit precise.

114.06. 
14.16.  
68.69 
6.08. 
73.60
2.90

So I've rounded them to what I thought was more reasonable.

Answer: Thanks!
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Section 4
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This section needs some improving.

In addition to summarising what was done in the paper, it might be
useful if you write a paragraph describing the weaknesses and strength
of the technique you have used. For example, obvious strengths are
that the method is quantitative and can be applied to low and high
redshift specrta and that the S/N of the high redshift spectra do not
need to have very high S/N. A weakness is that the size of the
systematic error instroduced by subtracting the light from the host
galaxy is difficult to quantify and that high reshift SNe are likely
to suffer more from this error that SNe at low redshift.

Also, I think you should add a paragraph on how the weakness could be
overcome - e.g. a specrtrum of the host without the SNe.

The follwing sentence seems to say the same thing as the previous one.

"This classification was confirmed by means of the {\sc ew}
measurements."

and then there is too much detail in the following sentences. This
amount of detail should not appear in the summary.

Answer: OK done
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"Prior to maximum light, Ca~{\sc ii}~H\&K {\sc ew}s show
a clear distinction between the values typically found for normal and
SN~1991T/SN1999aa-like SNe. The value measured for SN~2002fd ($
{\mbox{{\sc ew}}} $ = 73.60 $\pm$ 1.89) results consistent with that
of SN~1991T/SN~1999aa-like object ($< {\mbox{{\sc ew}}} >$ = 68.69,
$\sigma_{< {\mbox{\scriptsize {\sc ew}}} >}$ 6.08)."


I don't think the last paragraph is necessary. It is not the main point
of the paper, yet it is the final thing that is said.

Answer: I've removed it. 
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