Upon examining the initial content of both files, here are the potential issues identified based on the provided hint regarding "Missing information and unclear abbreviation scheme":

### Issue 1

**Issue**: "Missing detailed description of dataset fields in readme.md"

**Evidence**: The content from `readme.md` starts with:
```
# COVID-19 in USA

Number of Novel Corona Virus 2019 cases in USA

## About Dataset

### Context

Data is obtained from [COVID-19 Tracking project](https://covidtracking.com/) and [NYTimes](https://github.com/nytimes/covid-19-data). Sincere thanks to them for making it available to the public. 
...
```

**Description**: The provided `readme.md` content begins by mentioning the source of the dataset but does not include a detailed description or explanation of the columns (fields) present in the dataset (`us_states_covid19_daily.csv`). This omission could lead to confusion regarding what each column represents, particularly in terms of what is meant by terms like `probableCases`, `inIcuCurrently`, etc., which are crucial for accurate data analysis and interpretation.

### Issue 2

**Issue**: "Use of abbreviations without definition"

**Evidence**: The first line from `us_states_covid19_daily.csv` is:
```
date,state,positive,probableCases,negative,pending,totalTestResultsSource,totalTestResults,hospitalizedCurrently,hospitalizedCumulative,inIcuCurrently,inIcuCumulative,onVentilatorCurrently,onVentilatorCumulative,recovered,dataQualityGrade,lastUpdateEt,dateModified,checkTimeEt,death,hospitalized,dateChecked,totalTestsViral,positiveTestsViral,negativeTestsViral,positiveCasesViral,deathConfirmed,deathProbable,totalTestEncountersViral,totalTestsPeopleViral,totalTestsAntibody,positiveTestsAntibody,negativeTestsAntibody,...
```

**Description**: The CSV file header includes several abbreviations and terms that could be unclear without a proper definition or explanation. For example, terms like `inIcuCurrently`, `onVentilatorCurrently`, and abbreviations such as `Et` in `lastUpdateEt` might not be immediately understood by all users of the dataset. These abbreviations and terms should be clearly defined in the `readme.md` to ensure the dataset is accessible and understandable to a wide audience, including those not intimately familiar with COVID-19 specific terminology or the specific data collection practices of the referred sources.

To further enhance the analysis, it would be prudent to examine if there are any abbreviations or column headings within the CSV file that are not addressed or clarified in the `readme.md`. Let's proceed to search for any such discrepancies in detail.Upon closer inspection of the CSV file headers in `us_states_covid19_daily.csv`, the following additional potential issues can be highlighted, further emphasizing pressing concerns regarding "Missing information and unclear abbreviation scheme", as hinted.

### Issue 3

**Issue**: "Abbreviations and specific terms lack definition"

**Evidence**: Columns such as `fips`, `posNeg`, `lastUpdateEt`, and others like `totalTestResultsSource`, `dataQualityGrade`.

**Description**: The dataset includes specific abbreviations and terms, such as `fips` (which typically refers to Federal Information Processing Standards codes for geographic locations), and other column names like `posNeg` (which likely represents a summary column of positive and negative test results), and `lastUpdateEt` (which possibly indicates the last update time in Eastern Time), that are not explained in the provided `readme.md`. Definitions for these terms and an explanation of their relevance and calculation (if applicable) are necessary for users to fully understand and utilize the dataset correctly. It is critical to provide a glossary or expanded definitions for all such terms and abbreviations within the documentation to make the data accessible and comprehensible to all potential users.

### Issue 4

**Issue**: "Inconsistency and lack of clarity in time-related columns"

**Evidence**: Columns including but not limited to `date`, `lastUpdateEt`, `dateModified`, and `checkTimeEt`.

**Description**: The dataset features multiple columns related to dates and times (`date`, `lastUpdateEt`, `dateModified`, `checkTimeEt`), which could potentially lead to confusion without clear documentation. It is unclear whether all date/time fields follow the same format or timezone (except for the apparent reference to Eastern Time in `lastUpdateEt`). This lack of clarity could lead to misinterpretations of the dataset's temporal dimensions, thereby affecting analyses. Clear documentation on each time-related field, including the format and timezone, should be provided in the `readme.md` for consistency and to avoid confusion among users.

Given the concerns identified, it is necessary to revise and enhance the dataset's accompanying documentation (`readme.md`) to address these issues for clarity, completeness, and usability of the dataset.