I'm sorry to ask such an elementary question. I am wanting to know how to type the following symbol in LaTeX, it is written with a subscript 'l' in the image below,     I feel quite illiterate because I don't even know how to read this symbol. I have tried typing the (English) alphabet in various font styles but nothing matched.   Many thanks
I know what my symbol or character looks like, but I don't know what the command is or which math alphabet it came from. How do I go about finding this out?
With constant travel, is it possible to not have a tax residence? Why are there holes in the icing? Here is the proof I tried to weave while trying to prove this theorem:     Theorem. Every infinite subset of a countable set is countable.      Proof. Let $A$ be a countable set and $E\subset A$ be infinite. Then $A\thicksim\mathbb{N}$. This implies that there is a sequence $\left\{x_{n}\right\}_{n\in\mathbb{N}}$ where $x_{n}\in A$. Construct a sequence $\left\{n_{k}\right\}_{k\in\mathbb{N}}$ where $x_{n_{k}}\in A$, $n_{1}$ is the smallest positive integer such that $x_{n_{1}}\in A$, and $n_{k+1}&gt;n_{k}$. Then      $$ E=\bigcup_{k=1}^{\infty}x_{n_{k}}, $$      and $E$ is countable, because $E\thicksim\mathbb{N}$. $\blacksquare$   Is it convincing? hyperlink name with biblatex authoryear I am using biblatex with the authoryear styles.  So far I've been able to find everything I need easily in the excellent documentation, but I'm stuck on one thing.   With my current settings (below) citations only have the year hyperlinked to the bibliography entry. I think prior to using biblatex I would have the whole citation (authors + year) as a reference - I think this is easier to click etc. when browsing.  Is there an easy way to get this (or does it involve creating a new style).  \usepackage[style=authoryear,             bibstyle=authoryear,             citestyle=authoryear,             natbib=true,             hyperref=true,             backref=true,             abbreviate=true]{biblatex} ElasticSearch doesn't start after installing 5.6.4 I'm trying to follow the  (on my Ubuntu 10.04 VM).  The first step is:  sudo add-apt-repository ppa:linaro-maintainers/toolchain   But when I run that I get:  Error reading https://launchpad.net/api/1.0/~linaro-maintainers/+archive/toolchain: &lt;urlopen error [Errno 110] Connection timed out&gt;   I'm guessing the problem is with my configuration for my employer's proxy server, particularly for HTTPS.  When I opened  in Firefox, I got "The connection has timed out".  I then went into Firefox Preferences -> Advanced -> Network -> Settings... and set HTTP Proxy to "gateway" and Port to 8080, and checked "Use this proxy server for all protocols".  Then the page loaded.  This supports my theory.  I've tried setting the http_proxy and https_proxy environment variables (both lower and upper case):  $ set | grep -i proxy HTTPS_PROXY=https://gateway:8080 HTTP_PROXY=http://gateway:8080 http_proxy=http://gateway:8080 https_proxy=https://gateway:8080   I also tried changing them to:  $ set | grep -i proxy HTTPS_PROXY=gateway:8080 HTTP_PROXY=gateway:8080 http_proxy=gateway:8080 https_proxy=gateway:8080   And I tried adding this second line to /etc/apt/apt.conf:  Acquire::http::proxy "http://gateway:8080/"; Acquire::https::proxy "https://gateway:8080/";   But I continue to get the same error.  How do I troubleshoot this?  Update: I followed the instructions in the  to  and got further:  $ sudo add-apt-repository ppa:linaro-maintainers/toolchain Executing: gpg --ignore-time-conflict --no-options --no-default-keyring --secret-keyring /etc/apt/secring.gpg --trustdb-name /etc/apt/trustdb.gpg --keyring /etc/apt/trusted.gpg --primary-keyring /etc/apt/trusted.gpg --keyserver keyserver.ubuntu.com --recv 1DD749B890A6F66D050D985CF1FCBACA7BE1F97B gpg: requesting key 7BE1F97B from hkp server keyserver.ubuntu.com gpgkeys: HTTP fetch error 7: couldn't connect to host gpg: no valid OpenPGP data found. gpg: Total number processed: 0   I wonder if the "HTTP fetch error" means I also need to add "Defaults env_keep = http_proxy" to /etc/sudoers...  Update #2: I added:  Defaults env_keep="http_proxy" Defaults env_keep="https_proxy"   ...as in , but I still get the same "gpgkeys: HTTP fetch error 7: couldn't connect to host" error.  And this is curious:  $ sudo env | grep proxy https_proxy=https://gateway:8080   ...because http_proxy isn't there.  Any advice is appreciated.  Update #3: Since the host of my VM is a laptop, I took it home and tried there (with no proxies):  $ sudo add-apt-repository ppa:linaro-maintainers/toolchain Executing: gpg --ignore-time-conflict --no-options --no-default-keyring --secret-keyring /etc/apt/secring.gpg --trustdb-name /etc/apt/trustdb.gpg --keyring /etc/apt/trusted.gpg --primary-keyring /etc/apt/trusted.gpg --keyserver keyserver.ubuntu.com --recv 1DD749B890A6F66D050D985CF1FCBACA7BE1F97B gpg: requesting key 7BE1F97B from hkp server keyserver.ubuntu.com gpg: key 7BE1F97B: public key "Launchpad Linaro Overlay PPA" imported gpg: Total number processed: 1 gpg:               imported: 1  (RSA: 1)   It worked.  So problem is related to proxy configuration.  But I suppose I have a workaround. Given an instance of System.Reflection.Assembly. Someone is offering to pay me in a sort of sugar daddy/sugar baby arrangement. They want to make online deposits to me, and they're asking me for my online banking username and password. Is that information alone enough for them to be able to take my money out of my account, or am I safe? etoolbox and tabularx -- problem with `appto` I'm trying to print worksheets. I have already implemented an automatic numbering for subtasks. I use tabularx for my subtasks (see the MWE below).  Yesterday, I tried to define a new macro called \task that has one optional argument which is the amount of points you can obtain for this particular question. I would like these optional arguments to be gathered with etoolbox's \appto command so that I can print them with my \credits command.  So far, this seems to be ind of struggling as tabularx is working on the tables several times. Every time tabularx calculates the width of X columns the points are appended to \credits which leads to an incorrect list of points.  Is there any way I can solve this problem? I'm currently stucked with this issue.  Plus, I don't know why my \task command does work. Why is the counter subtask not affected by tabularx's several trials?  \documentclass{scrartcl}  \usepackage[utf8]{inputenc} \usepackage[T1]{fontenc}  \usepackage{etoolbox} \usepackage{booktabs} \usepackage{ltablex} \usepackage{xifthen}  \def\credits{} \newcounter{subtask} \setcounter{subtask}{1} \renewcommand{\thesubtask}{\alph{subtask})} \newcommand{\task}[1][]{%     \ifthenelse{\isempty{#1}}{%         \thesubtask%         \stepcounter{subtask}%     }{%         \thesubtask%         \gappto\credits{(#1)}%         \stepcounter{subtask}%     }% }  \begin{document} \begin{tabularx}{\linewidth}[l]{l@{\hspace*{1ex}}X}     \task[1]    &amp;   TEXT1\\     \task       &amp;   TEXT2\\     \task[3]    &amp;   TEXT3 \end{tabularx} \credits \end{document}       The solution given by David Carlisle below causes a table that is too wide. How can this be undone?  \documentclass{scrartcl}  \usepackage[utf8]{inputenc} \usepackage[T1]{fontenc}  \usepackage[a6paper, showframe=true]{geometry}  \usepackage{etoolbox} \usepackage{booktabs} \usepackage{ltablex} \usepackage{xifthen}  \def\credits{} \newcounter{subtask} \setcounter{subtask}{1} \renewcommand{\thesubtask}{\alph{subtask})} \makeatletter \newcommand{\task}[1][]{%     \ifx\hfuzz\@tempdima% %   % tabularx trial do nothing     \else%         \ifthenelse{\isempty{#1}}{%             \thesubtask%             \stepcounter{subtask}%         }{%             \thesubtask%                 \gappto\credits{(#1 BE)\\}%             \stepcounter{subtask}%         }%     \fi } \makeatother   \begin{document}  \begin{tabularx}{\linewidth}[l]{l@{\hspace*{1ex}}X}     \task[1]    &amp;   Some longer text that exceedes the line width.\\     \task[4]    &amp;   TEXT2\\     \task[3]    &amp;   TEXT3 \end{tabularx} \credits  \end{document} Accidently deleted boot option on Dell laptop I have a Dell laptop in which I have dual booted Ubuntu with Windows 10. Usually the laptop loads the Grub menu first.  Recently I had some problems with Windows Bitlocker: every time I open Windows I am prompted to enter the Bitlocker password. In trying to solve this, I accidentaly clicked Ubuntu in the "Delete Boot" option in the boot sequence. Now the laptop boots directly to Windows without first loading the Grub menu.  Luckily, when I restarted the system and clicked "add boot option" I found the efi folder in which the Ubuntu folder is present. In Ubuntu there is fwgrupx64.efi, grubx64.efi, grub.cfg, shimx64.efi, mmx64.efi, and BOOTX64.CSV. On clicking grubx64.efi it shows "Boot name not found".  How can I recover the Grub boot menu? Will tcpdump see packets that are being dropped by iptables? Electron flow and electric potential In the physics tutorial topic on current electricity it defines the positive terminal as the high potential terminal and the negative as the low potential. When talking about positive test charges this analogy makes sense, the charge moves from the +ve to the -ve where it loses potential till it has to be "topped" up by the cell.   What confuses me when they begin talking electrons. Using this analogy would mean that the electrons move from the -ve to the +ve but this means it would work against the electric field so the potential energy increases till it reaches the +ve terminal.   My question is how does this analogy, if it does, change to accommodate electrons? Does the electric field reverse so the -ve terminal is the high potential and the +ve the low potential? Where can I obtain an English dictionary with structured data? How to mount read-write an ext4 partition on Windows? I want to use ext4 on my external HDD, but it must be cross-platform. (At least Linux, Win7 &amp; WinXP).  Unfortunately, I haven't found any proper driver allowing Windows to WRITE to ext4. I've found , but it only reads ext4.     9. ext4 extent read-only, no  size truncating and expanding support   More:     Supported Ext3/4 features:         flexible inode size: > 128 bytes, up to block size   dir_index:    htree directory index   filetype:     extra file mode in dentry   large_file:   > 4G files supported   sparse_super: super block backup in group descriptor   uninit_bg:    fast fsck and group checksum   extent:       reading, writing with no extending.   journal:      only support replay for internal journal         Unsupported Ext3/4 features:         journal: log-based operations, external journal   extent: size truncating &amp; expanding, file deletion   flex_bg: first metadata group   EA (extended attributes), ACL support      Also, I have found a patch for Ext4Fsd v0.50 ():     New: Matt Wu has made a new release 0.50 at   ext2fsd.com.  Support for ext4 extents and fix   for BSOD on Windows 7.   I don't think it will be safe. Also I've read some words about writing ext4 in Windows could cause data loss on the disk...  What is the External HDD used for? - First, it will store backups, then family movies, pictures. Some music, and etc. It will be connected to a Raspberry Pi, if I finally receive it. It won't really move, just when it is used to migrate computer's data to a new one. The largest files it will store are Clonezilla disk images (I don't know, if they will be large files or not).  Can someone provide a solution for this problem? Or is there NO important enough difference between ext4 and ext3, and I should use ext3? - (If yes, then can I use Ext2Fsd for that ext3 mount?)  Thank you! I'm trying CTest in CMake in order to automatically run some of my tests using make test target. The problem is CMake does not "understand" that the test I'm willing to run has to be built since it is part of the project.  So I'm looking for a way to explicitly specify this dependency. Ubuntu 16.10 Dual Boot error - 'grub-efi-amd64-signed' package failed to install Whoa! What is this "Linked" thing? As per the title, what is this new feature? I have a chromebook series 5. I want to install Ubuntu onto a USB stick. When I downloaded Ubuntu onto my USB stick, it won't start up.  Do I first have to download Ubuntu onto my chromebook hard drive, open Ubuntu and then make USB stick bootable? And then return back to chrome?  Or is there a way to download directly onto USB and make the stick bootable?  I appreciate any help. In the  library, they are overloading the () operator.  Is this a convention in C++? For callbacks, etc.?  I have seen this in code of a co-worker (who happens to be a big Boost fan). Of all the Boost goodness out there, this has only led to confusion for me.  Any insight as to the reason for this overload? Short story identification: society partitioned off by high wall